Over the past few weeks I have been contemplating the purpose of this blog. I originally had the idea of starting it as a place to capture my thoughts and information about photography equipment, style and techniques, but it started to become too much of a Wikipedia page, and too little of a useful tool for practicing photographers. As such I am contemplating a change to the format.
I hope to have a new format or purpose for this blog soon. I'd love for it be more of a resource for amateur photographers who are starting off and want to learn about what I've tried, challenges I have encountered, some practice techniques, and maybe a little bit of what I was doing before of providing some technical knowledge about photography gear and styles (still important to know this information if you want to be a good photographer). I may also post some more photos that I have taken, complementary to my 365 page, and discuss what I did to take the shot, or challenges that I had. As you can tell I am still sorting it out. If you have any suggestions or ideas of what you would like to read about or see on this page, be sure to leave me a comment on this post.
During this time, I will be putting on hold any regular posts to this blog page. I will likely finish out the series on focal lengths in the next couple of weeks before picking a new format. For those of you who may have been hoping for the next series on information for beginners, that may still happen under the new format.
-Adam
P.s. My 365 blog will still be updated weekly (or as often as I am able) with new photos until I complete the challenge.
Monday, July 18, 2011
Monday, July 11, 2011
Focal Lengths, Part II: What Exactly Is Normal? – Capturing the World with Normal Lenses
A few weeks ago I started a short series of posts on the different focal lengths of lenses and what that means to photographers. In Part I, I talked about wide and ultra-wide angle lenses which consist of a short focal length. As such, these lenses produce angles of view greater than that of human vision. For photographers these lenses allow you to capture more of a scene from a shorter distance, but more importantly have a greater depth of field and produce a feeling a space between objects closer to the lens compared to those which are further away. In this week’s post, I am going to focus on lenses that fall in the normal range. For reference I am reproducing the same table of focal lengths from Part I.
As I defined in the last post on focal lengths, a normal lens, as accepted by photographers and lens manufacturers, is a lens with a focal length around that of 50mm on a 35mm frame. Normal lenses ultimately range from about 35mm up to around 75mm. The notable feature is that lenses in this range produce images approximate to human vision in spatial relationships as well as having an angle of view similar to the human eye. In actuality the range is not defined by human vision but actually by the relationship to the diagonal measurement of the film or digital frame. On a 35mm frame, the diagonal measurement is around 43-44mm, but for ease of definition is was agreed to make the standard length 50 mm on this frame size. It should be also noted that 50mm is relative to a 35mm frame size. For a 1.5x crop sensor, a focal length of 35mm is approximately equivalent to 50mm (actually 52.5mm, but who’s counting).
Normal lenses are pretty straightforward tools for a photographer and as such this post will be more brief than most of my others. As this focal length approximates human vision it can be both one of the easiest lens to use, and also one of the more challenging at the same time. What do I mean by that? As normal lenses approximates human vision, it can be easy for the photographer to look at a scene and approximate what that scene may look like in the photo by just using his/her eyes. The distance between foreground and background objects are “normal” rather than exaggerated when using a wide-angle lens or a telephoto lens. There is little distortion caused by the lens as well. Wide-angle lenses can exaggerated features of a subject by spacing them out, or making closer features appear larger than those further away. On the flipside, telephoto lenses tend to compress or flatten features. Normal lenses do neither and reproduce spatial relations and size as we are used to seeing. As a result a photographer can just look around and see what he will see (approximately) through the lens.
So this is why normal lenses can be easier to use, but I also said this can make them more challenging. What I mean by that is that a photographer, if going for an artistic approach, has to work differently to make a interesting photograph. No matter what lens or camera you are using you need to work on composition, subject matter, lighting, etc. However with a normal lens, you have to work on your subject matter using the same approximate view that every observer of the same scene would have and so therefore does not immediately present an added level of interest. For example, if you are 20 feet away from a tree with a camera with normal lens and stake a picture, you will accurately reproduce and image of the tree, but it will look the same way it would like you just stood there and looked with your eyes. If you used a wide angle lens to take the same shot from the same position, it may make the tree look bigger than it is as compared to the background the photo with the normal lens. If you used a telephoto lens, you may capture some small details on the tree that aren't seen well by the normal lens. Both the wide angle and telephoto are different than what an observer sees and so can add a level of intrigue. You may think that this is a disadvantage of lenses of normal focal length, and my post should not be read that way. It is merely a difference, but one that should be recognized. On the flip side, the normal angle of view also means it reproduces the scene more accurately when compared to human vision. Neither a wide angle or telephoto lens can do that. Again, just a difference. However, because it is reproducing the scene with a similar view to all other observers, the emphasis is put on what and how you capture the subject matter rather than the effect the different angle of view and the effect on spatial relationships that other focal length have. This can be done in numerous ways, that I won’t get into in this post, and is really what makes up personal style of a photographer. But that being said, using a normal lens means you can’t rely on the altered view of the world from using longer and shorter focal lengths to add a level of artistic appeal of your photo. Does this mean that shots taken with normal lenses are any less artistic than those of other focal lengths? Again, absolutely not. Some of the most wonderful photographs ever taken were taken with normal lenses. Henri Cartier-Bresson was famous for only using a 50mm lens for his photographs. It just means that you have to see the beauty and art in things that most observers overlook and then capture it in a way to display that beauty.
Normal lenses tend to be fast lenses, and cheaper than fast lenses of shorter and longer focal lengths. For those not familiar with the term, a fast lens is one with a large maximum aperture (f-number smaller than 2.8). As they have a larger opening to let in light a shorter, or faster, shutter speed can be used. This has three advantages. First off, the faster shutter speed can freeze the action better than a slower one. With a wide maximum aperture a faster shutter speed can be used which can freeze faster objects. The second advantage is low light performance. Fast lenses can produce sharp images in lighting situations where slower lenses will cause blur, particularly when shooting subjects that can move, or when shooting hand-held. The third advantage is the ability to produce an incredibly shallow depth of field. This can be used for both practical and artistic reasons, by drawing focus to the subject by blurring out the foreground and background subjects. A lens of f/2.8 already has a pretty shallow depth of field so you can imagine how shallow it is with a lens with an f/1.4 maximum aperture. This shallow depth of field is often used in portraiture. In the world of the 35mm frame, a 50mm lens is a little short for portraiture. Often for portraits you want a shallow depth of field and a slight telephoto to compress the features of the human subject while still looking natural. This makes for a more flattering look. However, using a cropped sensor DSLR, a 50mm lens is equivalent to a 75mm lens. Even better, a 60mm lens is equivalent to 90mm lens. Bother are great length for portraits (most pros agree that 85-105mm is the ideal range for portraits but 75mm is not that far off and still works well).
I mentioned they were cheaper than fast lenses of wider or longer focal lengths. In general this is true. The normal lens is technically easier to engineer than lenses with angle of view greater or narrower than normal. As such they tend to have fewer glass elements, are lighter and have a simpler design. This ease of engineering means that they can generally be had for a lower price. For example, Nikon’s fast 50mm f/1.4 prime is approximately $350. For comparison, an 85mm f/1.4 prime is about $600 and the same goes for a fast 28mm lens. Even better, Nikon, and most manufacturers make a 50mm f/1.8 which is only 2/3rds of a stop slower and can be had for a mere $125. These lenses still tend to be super sharp, and I think that every photographer should have one in their camera bag. Most major manufacturers usually make a version for cropped sensor cameras (typically a fast 35mm lens) as well as full frame sensor cameras (note that the 50mm will still work on a cropped sensor just fine, but will be equivalent to a 75mm lens).
As you can see, normal lenses are straightforward, yet powerful tools for the photographer. If you could only own one lens for your whole photographic career, it should be a fast, normal prime lens. It can accurately reproduce the world around you. If you can own two or more lenses for you career, one of them should still be a fast, normal prime lens. The simplicity of the lens, and advantages described above make it easy to go out and capture the world.
Lens Range | Focal Length (35 mm frame) | Focal Length (1.5x Crop Sensor) |
Ultra-Wide Angle | < 20 mm | < 14mm |
Wide Angle | 20mm - 35mm | 14mm – 24mm |
Normal | 35mm – 70mm | 24mm - 47mm |
Short Telephoto | 70mm – 105mm | 47mm - 70mm |
Telephoto | 105mm – 300mm | 70mm – 200mm |
Super Telephoto | > 300mm | > 200mm |
As I defined in the last post on focal lengths, a normal lens, as accepted by photographers and lens manufacturers, is a lens with a focal length around that of 50mm on a 35mm frame. Normal lenses ultimately range from about 35mm up to around 75mm. The notable feature is that lenses in this range produce images approximate to human vision in spatial relationships as well as having an angle of view similar to the human eye. In actuality the range is not defined by human vision but actually by the relationship to the diagonal measurement of the film or digital frame. On a 35mm frame, the diagonal measurement is around 43-44mm, but for ease of definition is was agreed to make the standard length 50 mm on this frame size. It should be also noted that 50mm is relative to a 35mm frame size. For a 1.5x crop sensor, a focal length of 35mm is approximately equivalent to 50mm (actually 52.5mm, but who’s counting).
Normal lenses are pretty straightforward tools for a photographer and as such this post will be more brief than most of my others. As this focal length approximates human vision it can be both one of the easiest lens to use, and also one of the more challenging at the same time. What do I mean by that? As normal lenses approximates human vision, it can be easy for the photographer to look at a scene and approximate what that scene may look like in the photo by just using his/her eyes. The distance between foreground and background objects are “normal” rather than exaggerated when using a wide-angle lens or a telephoto lens. There is little distortion caused by the lens as well. Wide-angle lenses can exaggerated features of a subject by spacing them out, or making closer features appear larger than those further away. On the flipside, telephoto lenses tend to compress or flatten features. Normal lenses do neither and reproduce spatial relations and size as we are used to seeing. As a result a photographer can just look around and see what he will see (approximately) through the lens.
So this is why normal lenses can be easier to use, but I also said this can make them more challenging. What I mean by that is that a photographer, if going for an artistic approach, has to work differently to make a interesting photograph. No matter what lens or camera you are using you need to work on composition, subject matter, lighting, etc. However with a normal lens, you have to work on your subject matter using the same approximate view that every observer of the same scene would have and so therefore does not immediately present an added level of interest. For example, if you are 20 feet away from a tree with a camera with normal lens and stake a picture, you will accurately reproduce and image of the tree, but it will look the same way it would like you just stood there and looked with your eyes. If you used a wide angle lens to take the same shot from the same position, it may make the tree look bigger than it is as compared to the background the photo with the normal lens. If you used a telephoto lens, you may capture some small details on the tree that aren't seen well by the normal lens. Both the wide angle and telephoto are different than what an observer sees and so can add a level of intrigue. You may think that this is a disadvantage of lenses of normal focal length, and my post should not be read that way. It is merely a difference, but one that should be recognized. On the flip side, the normal angle of view also means it reproduces the scene more accurately when compared to human vision. Neither a wide angle or telephoto lens can do that. Again, just a difference. However, because it is reproducing the scene with a similar view to all other observers, the emphasis is put on what and how you capture the subject matter rather than the effect the different angle of view and the effect on spatial relationships that other focal length have. This can be done in numerous ways, that I won’t get into in this post, and is really what makes up personal style of a photographer. But that being said, using a normal lens means you can’t rely on the altered view of the world from using longer and shorter focal lengths to add a level of artistic appeal of your photo. Does this mean that shots taken with normal lenses are any less artistic than those of other focal lengths? Again, absolutely not. Some of the most wonderful photographs ever taken were taken with normal lenses. Henri Cartier-Bresson was famous for only using a 50mm lens for his photographs. It just means that you have to see the beauty and art in things that most observers overlook and then capture it in a way to display that beauty.
Normal lenses tend to be fast lenses, and cheaper than fast lenses of shorter and longer focal lengths. For those not familiar with the term, a fast lens is one with a large maximum aperture (f-number smaller than 2.8). As they have a larger opening to let in light a shorter, or faster, shutter speed can be used. This has three advantages. First off, the faster shutter speed can freeze the action better than a slower one. With a wide maximum aperture a faster shutter speed can be used which can freeze faster objects. The second advantage is low light performance. Fast lenses can produce sharp images in lighting situations where slower lenses will cause blur, particularly when shooting subjects that can move, or when shooting hand-held. The third advantage is the ability to produce an incredibly shallow depth of field. This can be used for both practical and artistic reasons, by drawing focus to the subject by blurring out the foreground and background subjects. A lens of f/2.8 already has a pretty shallow depth of field so you can imagine how shallow it is with a lens with an f/1.4 maximum aperture. This shallow depth of field is often used in portraiture. In the world of the 35mm frame, a 50mm lens is a little short for portraiture. Often for portraits you want a shallow depth of field and a slight telephoto to compress the features of the human subject while still looking natural. This makes for a more flattering look. However, using a cropped sensor DSLR, a 50mm lens is equivalent to a 75mm lens. Even better, a 60mm lens is equivalent to 90mm lens. Bother are great length for portraits (most pros agree that 85-105mm is the ideal range for portraits but 75mm is not that far off and still works well).
I mentioned they were cheaper than fast lenses of wider or longer focal lengths. In general this is true. The normal lens is technically easier to engineer than lenses with angle of view greater or narrower than normal. As such they tend to have fewer glass elements, are lighter and have a simpler design. This ease of engineering means that they can generally be had for a lower price. For example, Nikon’s fast 50mm f/1.4 prime is approximately $350. For comparison, an 85mm f/1.4 prime is about $600 and the same goes for a fast 28mm lens. Even better, Nikon, and most manufacturers make a 50mm f/1.8 which is only 2/3rds of a stop slower and can be had for a mere $125. These lenses still tend to be super sharp, and I think that every photographer should have one in their camera bag. Most major manufacturers usually make a version for cropped sensor cameras (typically a fast 35mm lens) as well as full frame sensor cameras (note that the 50mm will still work on a cropped sensor just fine, but will be equivalent to a 75mm lens).
As you can see, normal lenses are straightforward, yet powerful tools for the photographer. If you could only own one lens for your whole photographic career, it should be a fast, normal prime lens. It can accurately reproduce the world around you. If you can own two or more lenses for you career, one of them should still be a fast, normal prime lens. The simplicity of the lens, and advantages described above make it easy to go out and capture the world.
Thursday, July 7, 2011
Reflections of a Lens – The Alternate World of Reflex Mirror Lenses
As promised earlier this week, here is my bonus post. I’m going to keep this one straightforward, first introducing you to what exactly a reflex mirror lens is, and then pointing out some advantages and disadvantages of this style lens compared to the standard refractive lens. This lens is most applicable to DSLR users as point-and-shoots have the lens built in so switching to a reflex lens is not possible.
Reflex mirror lenses, also known as simply reflex lenses or mirror lenses, use a different technique than refractive lenses to focus the light on the image sensor of a camera. Refractive lenses, or the standard design of lens you would think of if I were to just say “camera lens,” use glass lens elements to augment the path of the light that enters the end of the lens and focus it down on the image sensor of the camera. The only elements involved in the refractive lens design are shaped pieces of glass. However, a reflex mirror lens uses both glass elements and mirrors to bounce and augment the light path.
Technically speaking there are three major parts to a reflex lens: a front lens element, a collector element and a corrector element. If you were really picky you could group the front lens and the corrector as a single element as I’ll describe in just a moment, but for the purposes of this discussion I’ll address them as three. The front lens element gathers the light into the lens body similar to how the front lens of a refractive lens does. The collector, usually a concave mirror with a hole in the center, does exactly what its name applies. It collects the light gathered into the lens and then reflects it back toward the center of the front element, where the corrector element is located. The corrector element, often a mirror, but sometimes a mirror and lens combination then bounces the light path down through the hole in the center of the collector, through the aperture, and onto the image sensor or film. This is illustrated here:
Although I did not illustrate it, there can often be additional glass elements to further focus and correct the light located between the hole in the collector and the image sensor.
This design and process of using mirrors to focus the light was originally developed for use in telescopes, and is still used in most telescopes today from the small personal telescope to the large room sized telescopes used in observatories around the world. Although there are many variations, there are three design types that stand out as the most popular, particular for use in the lens for cameras. They are the Schmidt-Cassegrain design, Maksutov-Cassegrain design, and the Argunov Cassegrain design. These designs are all named after the people who developed the part of the lens, with the first name referring to the person who developed the design for the corrector and the second name for the design of the collector. As you can see, all three use the Cassegrain collector and as such I am only going to differentiate them by discussion the corrector element. If you are interested in the actual people behind these designs, I encourage you to look them up on the web, but I am not going to focus on them here.
The Schmidt corrector uses a very slightly convex front lens element and flat corrector mirror mounted on the back of the front element. This is a very common design found in the lenses made for cameras and in small amateur telescopes. The problem with the Schmidt design for camera lenses is that as the flat corrector has limited power to flatten the image and can cause aberration and distortion in the image. The Maksutov design uses a slightly concave front element and as such a slightly convex corrector mirror. The shape of the mirror helps to flatten the image and correct for aberration and distortion of the image. The last design, the Argunov, which is similar to the Schmidt, but uses additional glass elements in front of the corrector (in terms of the direction of the light path) to correct and better focus the light. Although this can produce better images, it is often only used in larger telescopes and fairly infrequently in camera lenses, although sometime additional elements are incorporated into some of the Maksutov designed lenses. All of these designs adjust the focus of the light be moving the mirrors closer together or farther apart.
So I don’t know about you, but I’ve had enough of me talking about the actual designs and the names of the people developed them. This blog is about cameras, lenses and taking photos, so I’m moving away from the technical and now talking about the advantages and disadvantages of this type of lens for photography.
On the surface, the advantage of reflex lenses appear to be very strong, and would make you wonder why there are not more of them used by photographers today. That may be more clear when I touch on the disadvantages, but let’s focus on the positives for a moment. The biggest advantage of reflex mirror lenses is simply stated as “more bang for your buck.” What I mean by this, is that these lenses can pack a much longer focal length into a package which is not only smaller and lighter, but also cheaper than the equivalent focal length in refractive lens. How is this so? Well if you look at the design above you’ll notice that the light enters the lens, travels the majority of the length of the lens to the collector, where it is reflected the majority of the length back to the corrector mirror before traveling the length of the lens again to the image sensor. This “folded” light path means you can have a lens body that is a fraction of the length of a standard refractive lens. The collector mirror and the concave shape also helps to magnify the image even more so the length of lens is even shorter. Additionally as there are few heavy glass elements, and only a couple of mirrors, the weight of the lens is much lighter. In a refractive design, a 500mm lens can measure nearly 16 inches in length and way upwards of 9 lbs. I don’t know about you, but that’s not a lens you can carry around and shoot without the assistance of a tripod of a monopod. Those refractive lenses are the ones you see on the side of a baseball game or a on the sideline of a football field. That’s a big lens to move around. Additionally, not just because of their weight, but because of their length, they have major issues with shake caused by the photographers hands, the wind or the action of the camera which is another reason form amble support. The same focal length of a reflex lens can measure only 4 inches in length and weigh just a little over a pound. That is a huge difference, and can mean being tied to a tripod/monopod or potentially being able to handhold a lens with major magnification power. As a major bonus, the reflex lens may only cost a few hundred dollars where the refractive lens could easily cost you upwards of $8,000.
Another advantage of these lenses is that they do not have issue with chromatic aberration, or color shifting, that often plagues long refractive lenses. Because the light is not passing through a series of spherical glass elements, but is rather being bounced between mirrors, the colors tend to stay true across the whole image, even at the edges where CA is usually an issue.
So why then would anybody spend $8,000 on a refractive lens that weights a ton and is tough to maneuver when they could have lens they could walk around with that only weight around and costs just a few hundred bucks? Here’s why. Quality. Reflex lenses have major drawback when it comes to image quality, and I’m going to touch on a few of them here.
As I mentioned above, reflex lens correctors, in addition to reflecting the light to the focal plane, are designed to help eliminate some of the aberration, in the form of distortion, that is inherent in this lens design. With that being said, there are no perfect correctors and there is still some distortion which is different than the typical “pincushion” distortion seen in longer focal length refractive lenses. This distortion for many photographers is unacceptable and there is little you can do in post processing to hide it. However, that is all in the eye of the beholder. A strong image will often make slight issues with aberration appear non-existent and so I personally do not hold this as such an issue as a professional looking for perfection would. I’m just looking to capture good and interesting photos as I work my way up to seeking perfection (at which point I too would probably not use a reflex lens). Also and I don’t have $8,000-$10,000 do drop on a refractive lens.
The second major drawback is a lack of resolution and contrast. The reflex design, the fact that the center of the light bath is blocked by the corrector mirror and the reflected light has a hole due to the collector mirror, can actually lower the overall resolution and particularly the contrast of the lens. This is fairly evident when you use one. Your photos do come out a little flat looking. Contrast can always be boosted in post-processing, but you don’t want to rely on post-processing to get a good image. This is also dependent on what and where you are shooting. Due to their focal length, reflex lenses work great for capturing close shots of the moon and other celestial bodies. The dark sky and bright bodies are not as affected by the lower contrast of the lens, although, it is still noticeable (just not as much). Overall, I find this to be the biggest drawback of this lens design, but I’ll touch on whether or not I think this is enough to completely avoid these lenses a little later on in this post.
Another big drawback is the fixed aperture design of reflect lenses. Due to the design and having the center of the light path blocked, a variable aperture design is not possible in these reflex lenses. As such, each lens has a fixed aperture, and it is usually fairly slow. For example, it is possible to to get a 500mm lens with an f/6.3 aperture or and f/8 aperture, but that aperture is the only option. For longer lenses, the aperture gets smaller. Most 1000mm lenses have a fixed aperture of f/11. With a long focal length, these small apertures can make shooting pretty difficult and could potentially ruin the benefit of potentially handholding the lens. Nikon used to make a 500mm reflex lens with an f/5.6 aperture, but this was the fastest lens I’ve seen and it is still a full stop slower than typical 500mm refractive lenses. Practically speaking, this is the feature of these lenses that bugs me the post, because when I typically shoot, the aperture is typically the setting I focus on first, and then I check my shutter speeds. I love have control over the depth of field so this is my biggest dislike about these lenses.
The last major disadvantage to these lenses is the bokeh, or the out of focus area in a photograph, can have a funny donut shape to it. This donut bokeh can be distracting to the image, and many find it displeasing in general. I personally don’t mind it and think it can add some interesting effects to some photos, but I would really like to be able to turn it on and off (I know this is not an option, but I’m just saying if it was an option, I would want it) depending on what scene I was shooting. The best thing to do is to look up images online which were shot with reflex lenses and decide for yourself if it really is personal preference. I should also highlight, that due to the narrower fixed apertures in reflex lenses, in many situations, particularly those that are evenly lit, the bokeh is not all the pronounces. However if you have a spot of bright light, for instance the sun reflecting off the water, or a street light in a scene at dusk, the bokeh will be visible.
So as you can see, the advantages of these reflex lenses are pretty great, but the disadvantages may outweigh them (depending on the photographer). Reflex lenses, although have been made for shorter focal length is the past, really are not made any more for focal lengths less than 400mm. Without the benefit of the small package for a large focal length, the more those disadvantages are weighted and most companies understand this. They have also fallen out of favor with the big lens manufacturers who would rather focus on tweaking their higher quality refractive lenses than spending time making reflex lenses. Both Canon and Nikon used to make reflex lenses and you can still find them used for fairly good prices. Nikon made a 500mm, 1000mm and even a 2000mm lens under its Reflex-Nikkor lineup. The 1000mm and particularly the 2000mm lenses are very rare (the 2000mm is also a beast of a lens) and often still fetch prices in the thousands. The 500mm came in a few varieties and can still be found for a few hundred dollars (although those prices can be affected by collectors). 3rd party manufacturers such as Vivitar, Samyang and Opteka still make manual focus reflex lenses in 500mm and 800mm lengths. The only first party manufacturer of reflex lenses is Sony, which they inherited from their acquisition of Minolta. Their 500mm is probably one of the better lenses on the market today and it is the only reflex lens with autofocus. This lens works on their Alpha lineup of DSLRS.
If you venture outside of the U.S. market, you can find reflex lens under the Rubinar brand. These lenses are Russian-made and are some of the best reflex lenses out there (but still not rivaling high-end refractive lenses). They are made using the same design as used by the company MTO which was started by Dmitri Dimitriev Maksutov, of the same fame as the Maksutov-Cassegrain lens design. The downside of the MTOs as well as the Rubinar is the weight. These lenses use a lot of metal and as such tend to weight more than those made by other manufacturers. I personally own two MTOs: a 550mm f/8 MTO-500 and a beastly 1100mm f/10.5 MTO-1000A. The 1000A weighs about 8 lbs which definitely requires a tripod (but still shy of the 9 lbs for a 500mm refractive lens). They both use an M42 mount (see this post for more on adapting lenses). I picked up both of these lenses on EBay from sellers in Russia. They are about 40 years old, but still are in great working order.
So you now know that I own two of these reflex style lenses, so you must think I am going to tell you to go out and get one. Well, not exactly. As I have said a few times in this post, a lot of the features, advantages, and disadvantages of this style of lens are really personal choices by the photographer. These lenses are certainly not for everyone. I would say that if you have a desire to get out and shoot with some long glass and are not in the financial position or have the desire to drop $8,000-$10,000 on some long refractive glass, then give these a try (they are also much better than some of the junk refractive glass that is often sold under off-brands for cheap on EBay…don’t buy those). If you are looking for top of the line image quality, you are not going to get that out of a reflex lens, but that does not mean you can’t take great, interesting photos. Remember there’s currently a whole slew of photographers making a name for themselves today with exhibits filled with photos taken with toy cameras, so technical image quality is not always everything. So as you can tell, I’m not going to tell you to go buy one, or recommend them whole-heartedly, but I am also not going to completely trash them either. If you have potential need for a long lens, or a desire to try one, then pick one up and see how it goes. It certainly is one of the less expensive options to try out in the world of photography and may open your eyes to something you enjoy. Whatever you decide to do, go out and capture the world around you.
Reflex mirror lenses, also known as simply reflex lenses or mirror lenses, use a different technique than refractive lenses to focus the light on the image sensor of a camera. Refractive lenses, or the standard design of lens you would think of if I were to just say “camera lens,” use glass lens elements to augment the path of the light that enters the end of the lens and focus it down on the image sensor of the camera. The only elements involved in the refractive lens design are shaped pieces of glass. However, a reflex mirror lens uses both glass elements and mirrors to bounce and augment the light path.
Technically speaking there are three major parts to a reflex lens: a front lens element, a collector element and a corrector element. If you were really picky you could group the front lens and the corrector as a single element as I’ll describe in just a moment, but for the purposes of this discussion I’ll address them as three. The front lens element gathers the light into the lens body similar to how the front lens of a refractive lens does. The collector, usually a concave mirror with a hole in the center, does exactly what its name applies. It collects the light gathered into the lens and then reflects it back toward the center of the front element, where the corrector element is located. The corrector element, often a mirror, but sometimes a mirror and lens combination then bounces the light path down through the hole in the center of the collector, through the aperture, and onto the image sensor or film. This is illustrated here:
Although I did not illustrate it, there can often be additional glass elements to further focus and correct the light located between the hole in the collector and the image sensor.
This design and process of using mirrors to focus the light was originally developed for use in telescopes, and is still used in most telescopes today from the small personal telescope to the large room sized telescopes used in observatories around the world. Although there are many variations, there are three design types that stand out as the most popular, particular for use in the lens for cameras. They are the Schmidt-Cassegrain design, Maksutov-Cassegrain design, and the Argunov Cassegrain design. These designs are all named after the people who developed the part of the lens, with the first name referring to the person who developed the design for the corrector and the second name for the design of the collector. As you can see, all three use the Cassegrain collector and as such I am only going to differentiate them by discussion the corrector element. If you are interested in the actual people behind these designs, I encourage you to look them up on the web, but I am not going to focus on them here.
The Schmidt corrector uses a very slightly convex front lens element and flat corrector mirror mounted on the back of the front element. This is a very common design found in the lenses made for cameras and in small amateur telescopes. The problem with the Schmidt design for camera lenses is that as the flat corrector has limited power to flatten the image and can cause aberration and distortion in the image. The Maksutov design uses a slightly concave front element and as such a slightly convex corrector mirror. The shape of the mirror helps to flatten the image and correct for aberration and distortion of the image. The last design, the Argunov, which is similar to the Schmidt, but uses additional glass elements in front of the corrector (in terms of the direction of the light path) to correct and better focus the light. Although this can produce better images, it is often only used in larger telescopes and fairly infrequently in camera lenses, although sometime additional elements are incorporated into some of the Maksutov designed lenses. All of these designs adjust the focus of the light be moving the mirrors closer together or farther apart.
So I don’t know about you, but I’ve had enough of me talking about the actual designs and the names of the people developed them. This blog is about cameras, lenses and taking photos, so I’m moving away from the technical and now talking about the advantages and disadvantages of this type of lens for photography.
On the surface, the advantage of reflex lenses appear to be very strong, and would make you wonder why there are not more of them used by photographers today. That may be more clear when I touch on the disadvantages, but let’s focus on the positives for a moment. The biggest advantage of reflex mirror lenses is simply stated as “more bang for your buck.” What I mean by this, is that these lenses can pack a much longer focal length into a package which is not only smaller and lighter, but also cheaper than the equivalent focal length in refractive lens. How is this so? Well if you look at the design above you’ll notice that the light enters the lens, travels the majority of the length of the lens to the collector, where it is reflected the majority of the length back to the corrector mirror before traveling the length of the lens again to the image sensor. This “folded” light path means you can have a lens body that is a fraction of the length of a standard refractive lens. The collector mirror and the concave shape also helps to magnify the image even more so the length of lens is even shorter. Additionally as there are few heavy glass elements, and only a couple of mirrors, the weight of the lens is much lighter. In a refractive design, a 500mm lens can measure nearly 16 inches in length and way upwards of 9 lbs. I don’t know about you, but that’s not a lens you can carry around and shoot without the assistance of a tripod of a monopod. Those refractive lenses are the ones you see on the side of a baseball game or a on the sideline of a football field. That’s a big lens to move around. Additionally, not just because of their weight, but because of their length, they have major issues with shake caused by the photographers hands, the wind or the action of the camera which is another reason form amble support. The same focal length of a reflex lens can measure only 4 inches in length and weigh just a little over a pound. That is a huge difference, and can mean being tied to a tripod/monopod or potentially being able to handhold a lens with major magnification power. As a major bonus, the reflex lens may only cost a few hundred dollars where the refractive lens could easily cost you upwards of $8,000.
Another advantage of these lenses is that they do not have issue with chromatic aberration, or color shifting, that often plagues long refractive lenses. Because the light is not passing through a series of spherical glass elements, but is rather being bounced between mirrors, the colors tend to stay true across the whole image, even at the edges where CA is usually an issue.
So why then would anybody spend $8,000 on a refractive lens that weights a ton and is tough to maneuver when they could have lens they could walk around with that only weight around and costs just a few hundred bucks? Here’s why. Quality. Reflex lenses have major drawback when it comes to image quality, and I’m going to touch on a few of them here.
As I mentioned above, reflex lens correctors, in addition to reflecting the light to the focal plane, are designed to help eliminate some of the aberration, in the form of distortion, that is inherent in this lens design. With that being said, there are no perfect correctors and there is still some distortion which is different than the typical “pincushion” distortion seen in longer focal length refractive lenses. This distortion for many photographers is unacceptable and there is little you can do in post processing to hide it. However, that is all in the eye of the beholder. A strong image will often make slight issues with aberration appear non-existent and so I personally do not hold this as such an issue as a professional looking for perfection would. I’m just looking to capture good and interesting photos as I work my way up to seeking perfection (at which point I too would probably not use a reflex lens). Also and I don’t have $8,000-$10,000 do drop on a refractive lens.
The second major drawback is a lack of resolution and contrast. The reflex design, the fact that the center of the light bath is blocked by the corrector mirror and the reflected light has a hole due to the collector mirror, can actually lower the overall resolution and particularly the contrast of the lens. This is fairly evident when you use one. Your photos do come out a little flat looking. Contrast can always be boosted in post-processing, but you don’t want to rely on post-processing to get a good image. This is also dependent on what and where you are shooting. Due to their focal length, reflex lenses work great for capturing close shots of the moon and other celestial bodies. The dark sky and bright bodies are not as affected by the lower contrast of the lens, although, it is still noticeable (just not as much). Overall, I find this to be the biggest drawback of this lens design, but I’ll touch on whether or not I think this is enough to completely avoid these lenses a little later on in this post.
Another big drawback is the fixed aperture design of reflect lenses. Due to the design and having the center of the light path blocked, a variable aperture design is not possible in these reflex lenses. As such, each lens has a fixed aperture, and it is usually fairly slow. For example, it is possible to to get a 500mm lens with an f/6.3 aperture or and f/8 aperture, but that aperture is the only option. For longer lenses, the aperture gets smaller. Most 1000mm lenses have a fixed aperture of f/11. With a long focal length, these small apertures can make shooting pretty difficult and could potentially ruin the benefit of potentially handholding the lens. Nikon used to make a 500mm reflex lens with an f/5.6 aperture, but this was the fastest lens I’ve seen and it is still a full stop slower than typical 500mm refractive lenses. Practically speaking, this is the feature of these lenses that bugs me the post, because when I typically shoot, the aperture is typically the setting I focus on first, and then I check my shutter speeds. I love have control over the depth of field so this is my biggest dislike about these lenses.
The last major disadvantage to these lenses is the bokeh, or the out of focus area in a photograph, can have a funny donut shape to it. This donut bokeh can be distracting to the image, and many find it displeasing in general. I personally don’t mind it and think it can add some interesting effects to some photos, but I would really like to be able to turn it on and off (I know this is not an option, but I’m just saying if it was an option, I would want it) depending on what scene I was shooting. The best thing to do is to look up images online which were shot with reflex lenses and decide for yourself if it really is personal preference. I should also highlight, that due to the narrower fixed apertures in reflex lenses, in many situations, particularly those that are evenly lit, the bokeh is not all the pronounces. However if you have a spot of bright light, for instance the sun reflecting off the water, or a street light in a scene at dusk, the bokeh will be visible.
So as you can see, the advantages of these reflex lenses are pretty great, but the disadvantages may outweigh them (depending on the photographer). Reflex lenses, although have been made for shorter focal length is the past, really are not made any more for focal lengths less than 400mm. Without the benefit of the small package for a large focal length, the more those disadvantages are weighted and most companies understand this. They have also fallen out of favor with the big lens manufacturers who would rather focus on tweaking their higher quality refractive lenses than spending time making reflex lenses. Both Canon and Nikon used to make reflex lenses and you can still find them used for fairly good prices. Nikon made a 500mm, 1000mm and even a 2000mm lens under its Reflex-Nikkor lineup. The 1000mm and particularly the 2000mm lenses are very rare (the 2000mm is also a beast of a lens) and often still fetch prices in the thousands. The 500mm came in a few varieties and can still be found for a few hundred dollars (although those prices can be affected by collectors). 3rd party manufacturers such as Vivitar, Samyang and Opteka still make manual focus reflex lenses in 500mm and 800mm lengths. The only first party manufacturer of reflex lenses is Sony, which they inherited from their acquisition of Minolta. Their 500mm is probably one of the better lenses on the market today and it is the only reflex lens with autofocus. This lens works on their Alpha lineup of DSLRS.
If you venture outside of the U.S. market, you can find reflex lens under the Rubinar brand. These lenses are Russian-made and are some of the best reflex lenses out there (but still not rivaling high-end refractive lenses). They are made using the same design as used by the company MTO which was started by Dmitri Dimitriev Maksutov, of the same fame as the Maksutov-Cassegrain lens design. The downside of the MTOs as well as the Rubinar is the weight. These lenses use a lot of metal and as such tend to weight more than those made by other manufacturers. I personally own two MTOs: a 550mm f/8 MTO-500 and a beastly 1100mm f/10.5 MTO-1000A. The 1000A weighs about 8 lbs which definitely requires a tripod (but still shy of the 9 lbs for a 500mm refractive lens). They both use an M42 mount (see this post for more on adapting lenses). I picked up both of these lenses on EBay from sellers in Russia. They are about 40 years old, but still are in great working order.
So you now know that I own two of these reflex style lenses, so you must think I am going to tell you to go out and get one. Well, not exactly. As I have said a few times in this post, a lot of the features, advantages, and disadvantages of this style of lens are really personal choices by the photographer. These lenses are certainly not for everyone. I would say that if you have a desire to get out and shoot with some long glass and are not in the financial position or have the desire to drop $8,000-$10,000 on some long refractive glass, then give these a try (they are also much better than some of the junk refractive glass that is often sold under off-brands for cheap on EBay…don’t buy those). If you are looking for top of the line image quality, you are not going to get that out of a reflex lens, but that does not mean you can’t take great, interesting photos. Remember there’s currently a whole slew of photographers making a name for themselves today with exhibits filled with photos taken with toy cameras, so technical image quality is not always everything. So as you can tell, I’m not going to tell you to go buy one, or recommend them whole-heartedly, but I am also not going to completely trash them either. If you have potential need for a long lens, or a desire to try one, then pick one up and see how it goes. It certainly is one of the less expensive options to try out in the world of photography and may open your eyes to something you enjoy. Whatever you decide to do, go out and capture the world around you.
Monday, July 4, 2011
AI – Not Just a Movie by Steven Spielberg
Before I get started, I need to be up front and honest about today’s post. Although I am a Nikon guy, I have been trying to keep my posts general enough, or at least cover multiple brands, so that it has some relevance to photographers who don’t shoot Nikon. With that being said, today’s post is specifically for photographers who use Nikon SLRs. Stay tuned though as to make up for a post I was not able to get up a couple of weeks ago, I will be having a special edition post on Thursday where I’ll be talking about reflex mirror lenses and whether or not they are worth it. Also, in coming weeks I am going to continue my series on focal lengths followed up a new series (beginners are going to pay attention to that one). As always, I may not do the series in consecutive weeks to keep it interesting for readers who may not be interested in a series that lasts for a month before getting on to a different topic. Now on to today’s post about what the heck AI is in terms of Nikon lenses and how to make use of your older lenses that may not have it.
As mentioned above, this week’s post is really only relevant to the users of Nikon SLR and DSLRs. The topic is automatic indexing, or AI. I know with a topic like that you are on the edge of your seat (sarcasm abounds), but please bear with me as this is very relevant, may prevent you from breaking your camera, and may save you some money (more interested now?). Back in my post on lens mounts, I stated that Nikon had not really changed their lens mounting system, known as the F-mount, since its inception in 1959. This is a fantastic feature of the Nikon system and for Nikon users as it means that lenses that came out from the point on can be used on the vast majority of Nikon camera bodies including today’s modern DSLRs. Well, that is mostly true, there is one big caveat to that feature. In 1977, Nikon added a feature to its camera system that would be the only change that really affected the ability to use a lens from 1959 on a camera body made in 1978, or 1994, or 2011….you get the point. This feature was known as automatic-indexing, or AI for short. For the purposes of this post and as you look it up on the web, lenses before 1977 will be referred to as non-AI or pre-AI, lenses after will be referred to as AI lenses, and those that have been converted with be known as AI’d lenses. Lenses after that each have their of official letter designations (such as AIs, AF-I, AF-D, AF-S, etc). All of these terms are pretty standard in the Nikon community.
So what is automatic indexing, and why do you need to care? Well, to answer the second part in brief, you don’t need to care if you don’t use any lenses that pre-date 1977, but still read on as you may find a more inexpensive way to get some good glass. If you are really knew to cameras and only used DSLR and CPU based lenses, you may not know that before the chip was placed in the lenses back in the late 80s and early 90s, the camera had no idea what that aperture was on the lens without a mechanical linkage. (If you are really new to it and have lenses without aperture rings, you may not even realize that up until the last decade or so, the aperture was completely controlled by a ring on the lens body.) This linkage between the lens and body had a couple of different executions in the history of Nikon SLRs.
The Nikon F camera introduced in 1959 (after which the F-mount was named) utilized a pin-and-yoke system to tell the camera what aperture was currently in use on the lens. There was a lever with a bin mountd just above the throat of the camera where the lens attached. There was a corresponding bracket on the lens, specifically on the aperture ring, called a yoke. When attached the lens you needed to make sure the pin was captured by the yoke on the lens. As you turned the aperture ring, the yoke would move the pin, and this would inform the metering system on the camera as to what aperture was in use. However, because there was no CPU or way of telling the camera what lens and how many f-stops it had for its aperture range, the photographer had “index” the lens. The yoke on the lens was mounted above f/5.6. When the photographer mounted the lens, he/she had to turn the aperture ring all the way to the widest setting and then back to the aperture he/she wanted to use. The distance the pin traveled would tell the camera what the actual f-stop was on the camera (essentially calibrating the metering system to the lens). If the photographer didn’t index the lens, the meter would be way off and so would the exposures. Well as you can guess, this could become a common problem and as you were shooting with film, there was no way to know until you developed a roll to find all of your photos were either under or over-exposed.
To help aid this process, in 1977, Nikon introduced the automatic-indexing system on its line of cameras and lenses. This feature would do exactly as it sounds: it would index the lens automatically so all the photographer had to do was attach the lens and shoot away. It accomplished this by inserting a tab on the outside of the flange where the lens attached to the camera body. The aperture ring had a indexing ridge on it (essentially ring on the AI lens was narrower than the non-AI ring except for a ridge that was left at the same length). This ridge would engage the indexing tab on the body when the lens was inserted and inform the camera meter what f/stop the lens was set at. No manual indexing was required. In addition to the addition of the metering tab and the ridge on the lens, the AI lenses also had a second aperture scale in smaller number on the edge of the ring that could be seen through the viewfinder of some models of cameras. The yoke on the lens was left on for a couple of years, but was removed in 1979 as Nikon wanted people to move on to their newer cameras with AI and not preserve the old pin-and-yoke mechanism. Nikon did run a service to convert non-AI to AI lenses for a period of time (up until 1991) for a small cost which allowed many photographers to continue using the non-AI lenses they loved on their newer camera bodies.
Ok, great, so I’ve explained and given the basic history of the changeover from non-AI to AI, but how the heck does this affect you. This was decades ago, right? Again, if you don’t ever use an older lens, then it doesn’t really affect you at all. But, read on for good measure. Ever since the 1980s and 1990s, the majority of Nikon’s lenses have contained a computer chip. This chip told the camera what lens was on the camera, what aperture was set and, in some iterations, the distance from the camera to the subject. This chip communicated to the camera through a set of electrical contacts that Nikon placed around the bayonet of the lens and inside the flange on the camera body. However, in an effort to maintain compatibility with older lenses (again, a benefit of the Nikon system that Nikon recognizes their customers appreciate), they kept the metering tab on cameras all the way through to today. This means that the D7000 made in 2011 has a metering tab that would allow it to work properly with AI lenses made in 1977. Almost all of Nikon’s mid-range and higher end cameras (D300 and up) today have a metering tab and a minimum aperture contact (allows use of AF-D style lenses). As such, if you try to mount a non-AI lens on one of these camera bodies, it does not have room on the aperture ring to allow for the tab, and as such can cause the tab to bend, or break-off, essentially breaking part of the functionality of the camera. The lower mid-range cameras (D90 ,D7000, etc) do not have a metering tab, but do have a contact to tell the camera the lens is set at its minimum aperture which also can be damaged by the non-AI aperture ring. The entry-level line of cameras (D40, D40x, D60, D3000, D5000, D3100, D5100, etc.) do not have either metering tab or the minimum aperture contact. The entry-level line will only work properly with AF-S lenses where the AF motor is in the lens body. However, because they do not have a tab or contact on the mount, these entry-level cameras could accept lenses dating back to 1959 allowing the photographer to use them in complete manual mode (but no metering).
If you have a lens that pre-dates the 1977 introduction of AI, then you should not mount it on your new DSLR until you find out if it will accept it with no damage (you should check the manual anyways before mounting any lens just in case). I had one of these lenses that I used with my Nikon FG film camera. It is a Nikkor 28mm f/2.8 and it was made before 1977 (see below to tell quickly if your lens is AI or not). I really liked this lens and wanted to continue to use it on my D90, but because of the minimum aperture contact tab, I could not. And since Nikon no longer converted the lenses for a fee, I turned to a 3rd party to help solve my problem. I don’t make it a habit to promote one place over another on this blog and certainly do not get paid or any benefit from promoting another business or product, but I will tell you which place I have used for a specific service, and whether or not I had a good or bad experience. For this AI-conversion, I sent my lens off to John White (www.aiconversions.com). For a reasonable fee, John takes and machines down a section on the back end of the aperture ring to accommodate the metering tab on the camera. He then inserts a label with the secondary aperture scale mentioned above (only useful on some cameras made in the 1980s, but nice to have nonetheless). All and all it was a great experience and I would definitely consider using him again as the service was fast, reasonably priced and professionally done. If you are so inclined you could do this service yourself, but given the low cost of getting it done by someone who has done it before, I decided it was no worth the risk of doing it wrong and breaking my camera anyways, but you could certainly do it if you have better skills with tools than I do. Now I can use the lens on any of my cameras including my Nikon FG or even my father’s Nikkormat (pin-and-yoke style).
I mentioned above that reading this post could save you from accidentally breaking your camera by attaching a non-AI lens to your camera body which I explained above. However, I also mentioned that this could potentially save you money. If you are a person who likes manual focus and are looking for some good inexpensive Nikon lenses, then I highly suggest checking out online auctions or other sources for used gear and pick up some non-AI lenses. Since they lack compatibility with many modern cameras in their unmodified form, they often go for real cheap, but with some still fantastic glass (in fact many of the AI-s lenses still available from Nikon today are based off these non-AI lens designs). Then just send out the lens for conversion or do it yourself, and amazingly you have a usable inexpensive manual focus lens from Nikon. This may not be the best approach for you and I would only recommend it if you prefer older manual focus glass. If you are in that boat then this a good way to save some money without risking your camera.
So before I wrap up this post, I mentioned I would describe how to tell if the lens you have is non-AI or AI (or AI’d). The biggest give away is that the yoke on the non-AI lens is solid (no holes except the slot to accept the pin). It is possible the yoke will still be solid if the lens was previously converted to AI. If the yoke has additional holes (designed to let in more light to see the additional aperture scale on some cameras) then it is AI compatible. Also, on AI lenses you should be able to see the metering ridge on the back edge of the aperture ring. If the ring has a slot cut away, it is possible that it was AI converted (AI’d). If the ring is solid all the way around check some of the features before trying to mount it. As mentioned above, AI lenses also have a smaller, secondary set of aperture numbers toward the back edge of the aperture ring. If you only have ne set of larger numbers it is likely an non-AI lens. In many AI conversions these numbers will be added by way of a thin label. If you are buying a lens and are unsure about the AI status, ask the seller if the lens was converted or if they know when it was made. If they are reputable used lens dealer they will know and tell you (many will often taught that it has been converted as it justifies them selling it at a higher price), but always check the other features listed above. There are a couple of more ways which use the color of numbering of the smallest aperture on the scale, but they can vary so I won’t go into them. There are some other great sources on the web for more information of the progression from non-AI to AI, so please go check some of them out as well (as much as people in forums like to harp on Ken Rockwell, he does have a lot of good information on his site, www.kenrockwell.com). You can also always take a photo of the lens and post it in a forum, or send it off to a conversion service to ask them.
So that wraps up this week’s post. I promise to not have too many of these Nikon only posts, but I thought this was one that was relevant and important information. It also ties in to my posting in conjunction with the photos I’m taking as part of my 365 photo challenge. As I mentioned there will be another one a little later this week which will not be specific to any one brand. In the meantime, get out there and capture the world around you.
As mentioned above, this week’s post is really only relevant to the users of Nikon SLR and DSLRs. The topic is automatic indexing, or AI. I know with a topic like that you are on the edge of your seat (sarcasm abounds), but please bear with me as this is very relevant, may prevent you from breaking your camera, and may save you some money (more interested now?). Back in my post on lens mounts, I stated that Nikon had not really changed their lens mounting system, known as the F-mount, since its inception in 1959. This is a fantastic feature of the Nikon system and for Nikon users as it means that lenses that came out from the point on can be used on the vast majority of Nikon camera bodies including today’s modern DSLRs. Well, that is mostly true, there is one big caveat to that feature. In 1977, Nikon added a feature to its camera system that would be the only change that really affected the ability to use a lens from 1959 on a camera body made in 1978, or 1994, or 2011….you get the point. This feature was known as automatic-indexing, or AI for short. For the purposes of this post and as you look it up on the web, lenses before 1977 will be referred to as non-AI or pre-AI, lenses after will be referred to as AI lenses, and those that have been converted with be known as AI’d lenses. Lenses after that each have their of official letter designations (such as AIs, AF-I, AF-D, AF-S, etc). All of these terms are pretty standard in the Nikon community.
So what is automatic indexing, and why do you need to care? Well, to answer the second part in brief, you don’t need to care if you don’t use any lenses that pre-date 1977, but still read on as you may find a more inexpensive way to get some good glass. If you are really knew to cameras and only used DSLR and CPU based lenses, you may not know that before the chip was placed in the lenses back in the late 80s and early 90s, the camera had no idea what that aperture was on the lens without a mechanical linkage. (If you are really new to it and have lenses without aperture rings, you may not even realize that up until the last decade or so, the aperture was completely controlled by a ring on the lens body.) This linkage between the lens and body had a couple of different executions in the history of Nikon SLRs.
The Nikon F camera introduced in 1959 (after which the F-mount was named) utilized a pin-and-yoke system to tell the camera what aperture was currently in use on the lens. There was a lever with a bin mountd just above the throat of the camera where the lens attached. There was a corresponding bracket on the lens, specifically on the aperture ring, called a yoke. When attached the lens you needed to make sure the pin was captured by the yoke on the lens. As you turned the aperture ring, the yoke would move the pin, and this would inform the metering system on the camera as to what aperture was in use. However, because there was no CPU or way of telling the camera what lens and how many f-stops it had for its aperture range, the photographer had “index” the lens. The yoke on the lens was mounted above f/5.6. When the photographer mounted the lens, he/she had to turn the aperture ring all the way to the widest setting and then back to the aperture he/she wanted to use. The distance the pin traveled would tell the camera what the actual f-stop was on the camera (essentially calibrating the metering system to the lens). If the photographer didn’t index the lens, the meter would be way off and so would the exposures. Well as you can guess, this could become a common problem and as you were shooting with film, there was no way to know until you developed a roll to find all of your photos were either under or over-exposed.
To help aid this process, in 1977, Nikon introduced the automatic-indexing system on its line of cameras and lenses. This feature would do exactly as it sounds: it would index the lens automatically so all the photographer had to do was attach the lens and shoot away. It accomplished this by inserting a tab on the outside of the flange where the lens attached to the camera body. The aperture ring had a indexing ridge on it (essentially ring on the AI lens was narrower than the non-AI ring except for a ridge that was left at the same length). This ridge would engage the indexing tab on the body when the lens was inserted and inform the camera meter what f/stop the lens was set at. No manual indexing was required. In addition to the addition of the metering tab and the ridge on the lens, the AI lenses also had a second aperture scale in smaller number on the edge of the ring that could be seen through the viewfinder of some models of cameras. The yoke on the lens was left on for a couple of years, but was removed in 1979 as Nikon wanted people to move on to their newer cameras with AI and not preserve the old pin-and-yoke mechanism. Nikon did run a service to convert non-AI to AI lenses for a period of time (up until 1991) for a small cost which allowed many photographers to continue using the non-AI lenses they loved on their newer camera bodies.
Ok, great, so I’ve explained and given the basic history of the changeover from non-AI to AI, but how the heck does this affect you. This was decades ago, right? Again, if you don’t ever use an older lens, then it doesn’t really affect you at all. But, read on for good measure. Ever since the 1980s and 1990s, the majority of Nikon’s lenses have contained a computer chip. This chip told the camera what lens was on the camera, what aperture was set and, in some iterations, the distance from the camera to the subject. This chip communicated to the camera through a set of electrical contacts that Nikon placed around the bayonet of the lens and inside the flange on the camera body. However, in an effort to maintain compatibility with older lenses (again, a benefit of the Nikon system that Nikon recognizes their customers appreciate), they kept the metering tab on cameras all the way through to today. This means that the D7000 made in 2011 has a metering tab that would allow it to work properly with AI lenses made in 1977. Almost all of Nikon’s mid-range and higher end cameras (D300 and up) today have a metering tab and a minimum aperture contact (allows use of AF-D style lenses). As such, if you try to mount a non-AI lens on one of these camera bodies, it does not have room on the aperture ring to allow for the tab, and as such can cause the tab to bend, or break-off, essentially breaking part of the functionality of the camera. The lower mid-range cameras (D90 ,D7000, etc) do not have a metering tab, but do have a contact to tell the camera the lens is set at its minimum aperture which also can be damaged by the non-AI aperture ring. The entry-level line of cameras (D40, D40x, D60, D3000, D5000, D3100, D5100, etc.) do not have either metering tab or the minimum aperture contact. The entry-level line will only work properly with AF-S lenses where the AF motor is in the lens body. However, because they do not have a tab or contact on the mount, these entry-level cameras could accept lenses dating back to 1959 allowing the photographer to use them in complete manual mode (but no metering).
If you have a lens that pre-dates the 1977 introduction of AI, then you should not mount it on your new DSLR until you find out if it will accept it with no damage (you should check the manual anyways before mounting any lens just in case). I had one of these lenses that I used with my Nikon FG film camera. It is a Nikkor 28mm f/2.8 and it was made before 1977 (see below to tell quickly if your lens is AI or not). I really liked this lens and wanted to continue to use it on my D90, but because of the minimum aperture contact tab, I could not. And since Nikon no longer converted the lenses for a fee, I turned to a 3rd party to help solve my problem. I don’t make it a habit to promote one place over another on this blog and certainly do not get paid or any benefit from promoting another business or product, but I will tell you which place I have used for a specific service, and whether or not I had a good or bad experience. For this AI-conversion, I sent my lens off to John White (www.aiconversions.com). For a reasonable fee, John takes and machines down a section on the back end of the aperture ring to accommodate the metering tab on the camera. He then inserts a label with the secondary aperture scale mentioned above (only useful on some cameras made in the 1980s, but nice to have nonetheless). All and all it was a great experience and I would definitely consider using him again as the service was fast, reasonably priced and professionally done. If you are so inclined you could do this service yourself, but given the low cost of getting it done by someone who has done it before, I decided it was no worth the risk of doing it wrong and breaking my camera anyways, but you could certainly do it if you have better skills with tools than I do. Now I can use the lens on any of my cameras including my Nikon FG or even my father’s Nikkormat (pin-and-yoke style).
I mentioned above that reading this post could save you from accidentally breaking your camera by attaching a non-AI lens to your camera body which I explained above. However, I also mentioned that this could potentially save you money. If you are a person who likes manual focus and are looking for some good inexpensive Nikon lenses, then I highly suggest checking out online auctions or other sources for used gear and pick up some non-AI lenses. Since they lack compatibility with many modern cameras in their unmodified form, they often go for real cheap, but with some still fantastic glass (in fact many of the AI-s lenses still available from Nikon today are based off these non-AI lens designs). Then just send out the lens for conversion or do it yourself, and amazingly you have a usable inexpensive manual focus lens from Nikon. This may not be the best approach for you and I would only recommend it if you prefer older manual focus glass. If you are in that boat then this a good way to save some money without risking your camera.
So before I wrap up this post, I mentioned I would describe how to tell if the lens you have is non-AI or AI (or AI’d). The biggest give away is that the yoke on the non-AI lens is solid (no holes except the slot to accept the pin). It is possible the yoke will still be solid if the lens was previously converted to AI. If the yoke has additional holes (designed to let in more light to see the additional aperture scale on some cameras) then it is AI compatible. Also, on AI lenses you should be able to see the metering ridge on the back edge of the aperture ring. If the ring has a slot cut away, it is possible that it was AI converted (AI’d). If the ring is solid all the way around check some of the features before trying to mount it. As mentioned above, AI lenses also have a smaller, secondary set of aperture numbers toward the back edge of the aperture ring. If you only have ne set of larger numbers it is likely an non-AI lens. In many AI conversions these numbers will be added by way of a thin label. If you are buying a lens and are unsure about the AI status, ask the seller if the lens was converted or if they know when it was made. If they are reputable used lens dealer they will know and tell you (many will often taught that it has been converted as it justifies them selling it at a higher price), but always check the other features listed above. There are a couple of more ways which use the color of numbering of the smallest aperture on the scale, but they can vary so I won’t go into them. There are some other great sources on the web for more information of the progression from non-AI to AI, so please go check some of them out as well (as much as people in forums like to harp on Ken Rockwell, he does have a lot of good information on his site, www.kenrockwell.com). You can also always take a photo of the lens and post it in a forum, or send it off to a conversion service to ask them.
So that wraps up this week’s post. I promise to not have too many of these Nikon only posts, but I thought this was one that was relevant and important information. It also ties in to my posting in conjunction with the photos I’m taking as part of my 365 photo challenge. As I mentioned there will be another one a little later this week which will not be specific to any one brand. In the meantime, get out there and capture the world around you.
Monday, June 27, 2011
Adaptations – When Your Lens and Body Don’t See Eye-to-Eye
In a fairly length blog post back in May, I talked a lot about the different types of lens mounts, the differences between the manufacturers and some considerations when using those lenses on your camera body. At the end I mentioned I would follow up with a separate post about adapting lenses, with a particular focus on a combination that I have come to enjoy, the M42 lens on a Nikon camera body. I am going to focus on this combination as it takes into account several of the factors you would need to consider when adapting lenses. And even though I am talking primarily about the M42/Nikon combination, these aspects apply to adapting other types of lenses to other types of camera bodies, so please read on even if you use Canon and want to use a Nikon lens on your camera or any other combination.
Before I go on to specifics about adapting the M42 lens to a Nikon body, I am going to re-post the section with a bit of history and details on the M42 and M39 lenses below:
“M42 and M39 Universal Mounts – Although M42 and M39 mounts are different and were used by different companies, I grouped them together because they shared similar properties. The M## designation reflected the metric 42 or 39mm screw thread. Both used a thread pitch of 1mm. T-Mounts (see below) also have a 42mm diameter, however it uses a 0.75mm thread pitch and is not compatible with M42 cameras and vice versa. The M42 mount was first developed by Carl Zeiss back in the 1930s, and was adopted by many European, and particularly Russian camera and lens manufacturers. The M42 standard utilized a 45.46mm registration distance. As I mentioned above in the Pentax section, the Pentax camera company utilized the M42 mount as well. In the United States became known as the Pentax Universal Screw mount. The same occurred with the Praktica camera brand outside the US, however both are M42 universal screw mounts. The M39 screw mount was developed by Leica prior to the development of the Leica R bayonet mount and had a registration of only 28.8mm which is too short for many other cameras. Early Canon cameras used it (but called the J-mount) as did several of the Russian camera brands. The Zenit camera brand adopted the M39 configuration but extended the registration to 45.2mm. There is no visual difference between the mounts with different registration distances, so you must know for which one your particular M39 lens was designed.”
So know you have been refreshed on what an M42 mount is and a bit of the technical details. As you can tell by the description, a 42mm screw is not going to connect with the bayonet style receiving flange on a Nikon body, so an adapter must be used. Not all that surprisingly, the major camera manufacturer’s who also make lenses, do not make adapters to attach a different type of lens on their camera body. They want you to buy the equivalent type of lens from them with their mount. And, that’s a good business practice, but for the consumer and photographer it limits your world to lenses made from just one manufacturer. Now if I were limited to just using Nikon lenses, I would certainly get over it quickly, but knowing that there are some many different brands and types of lenses out there, I don’t want to be limited. For example, I have a Helios 44-2 58mm f/2 lens at home which uses an M42 lens mount. What is so special about it? It’s just a fast, normal prime lens. I could easily get the 50mm f/1.8D from Nikon (and I own that as well). So why would I want to attach this old lens to my new DSLR? Simple. The bokeh on this lens (a term for the quality of the out of focus area in front of and behind the subject that is in focus) has an awesome swirling pattern to it which I really like for some of my more artistic shots. The smooth bokeh on the Nikkor 50mm f/1.8 is great, but it doesn’t have the same effect. As an added bonus, because there are a lot of these old Russian lenses out there no new cameras today that accept M42 lenses, I was able to pick one up for cheap ($20) on Ebay and it is in flawless condition.
But what good is a fantastic lens for $20, if you can’t natively attach it to your camera, and your camera manufacturer doesn’t make an adapter to attach it? This is where general 3rd party manufacturers come in. There a slew of these 3rd party manufacturers who make adapters for just about any lens/camera combination where the connection is possible (for example Canon EOS lenses, due to their diameter, cannot be adapted to a Nikon body so no reputable manufacturer will make this type of adapter). These lens adapters are very simple in nature, being cut from aluminum, and consisting of the female attachment for the lens on one side and the male flange for the camera body on the other. Some manufacturers that are popular are Bower in the U.S. and Kood in the U.K., but there are many out there including some store brands which are just fine for simple adapters. They are usually sold for just a few dollars so if you get one brand and find there is some aspect that you don’t like about it (for example I have one adapter that does not lock into to the camera body properly) then there is not a whole lot lost and you can try another brand. Again, this is for the simple metal adapters (more on what is not a simple adapter in a minute).
Many lens combinations work really well with a simple adapter, for example mounting a Nikon lens on a Canon camera body. As the throat of the lens on the Nikon is smaller than the opening on the Canon there is no issue there. Additionally as the registration distance (for more on this see this post) for Nikon is longer than that for Canon, there is no issue with not being able to focus to infinity, however you may lose a little, but of focusing power on the shorter end. One thing to be weary of is the distance that the lens protrudes into the camera body. If one camera system is designed for a lens where the back element is deep in the body and you attach that lens to body where the system does not require the lens to stick into the body very deeply, you may end up with issues. The most common of these is that the reflex mirror actually hits the end of the lens which can do damage to the lens, but more likely could break the mirror in the camera (not something you want to fix). To avoid this, do your research online and look for groups on photography forums where these are discussed (such as Flickr or Photo.net). A few simple web searches will avoid you a whole lot of hassle before spending money on a lens that may end up breaking your camera.
Nikon, is actually one o the more challenging camera bodies to adapt lens to, but it also one of the safest. How so? First off, the opening or throat diameter on the Nikon body, is fairly narrow. As I mentioned in the earlier posts, Nikon has made very few changes to their mount since it came out in the 1950s and this “narrow” throat is one of the features that has been maintained. Why is this an issue? Most lenses with different mounts will still work as the throat is very similar to that of the Nikon. However some manufacturers, Canon with their EOS mount being the most recognizable of these brands, have a throat opening which is much wider than that of Nikon. As such, the end of the lens is too large to fit into the throat on a Nikon body. This is great for Canon users as they can use their Canon lenses and also use the narrower Nikon lenses which will mount deep enough in the body to make up the difference in registration distance with just a simple adapter. However, as you may be able ot tell from the other direction, Nikon users cannot use Canon EOS lenses on their bodies. The physics of it just don’t mix. A very complex adapter with lens elements would need to be developed, and the cost and headache of this type of adapter would not be worth the effort. As such, Nikon users are a little more limited in what lenses they can choose from when venturing outside of their brand. As noted by me, a Nikon user, this is very disappointing as Canon does have some great lenses I would like to try (although not enough to want to switch brands). I do not fault Canon or Nikon for this as it is just a product of the difference in design (at least I’ll be optimistic and say that this was not the intention of making the difference in design larger than any other two brands).
The second challenging part about adapting lenses to Nikon bodies is that the registration distance on a Nikon is 46.5mm and is longer than most other major camera manufacturers. By putting a lens on that is designed for a system with a shorter distance, you can be certain that you will not run into issues with the mirror hitting the lens. However, on the other side as the lenses were designed with a shorter registration distance in mind, you may actually lose the ability to focus to infinity (the lens is physically further away from the sensor and the stop that the manufacturer puts in the lens at infinity, will not allow the lens to be focused far enough to make up for that difference. This is exactly the issue of adapting my M42 lenses to my Nikon bodies. There are three main options when you run into this situation. You can use the lens as-is with a simple adapter without being able to focus to infinity, you can use a more complex adapter that uses an optical element to correct for the distance and allow for infinity focusing, or you can modify the stop in the lens to achieve infinity. There are advantages and disadvantages to each of these options. To explore these options, I will let you know what I have done on a few of my lenses.
The main advantage to using a lens as-is is that you do not need to modify any part of the lens, or add additional glass between the lens and the image sensor. By adding in more glass you risk the potential for degrading the quality of the image produced by the lens as every time you pass light through another element, you take this risk. Also, as the adapters are made by 3rd party manufacturers, you risk that the glass used does not have the same quality as the glass in the lens itself. Just as a chain is only as good as its weakest link, a lens is only as good as its worst element. I have a Pentax 50mm f/4 macro lens with an M42 mount, which I picked up for $50 on EBay. It is a fantastic lens with some great bokeh. As it is used for macro work, I use it with a simple adapter and no additional glass element as all of my work involves focusing close and rarely want to use it to focus to infinity. This maintains the optical quality I want for the fine details of macro work while sacrificing a function of the lens that I do not use often for macro work. For this situation this was the best option for me.
The second option is to use an adapter that uses a correcting element to achieve infinity focus. The advantage here is obviously you do not need to modify anything and you can have infinity focus. The drawback is that you are introducing an additional piece of glass between the lens and the sensor. Depending on the adapter you get, this may be just fine, but is also may cause degradation in the image quality of the lens. Often these elements do not have the same quality or coatings as the elements used in the lens. This type of adapter is more expensive than the simple adapters, so going by trial and error as mentioned above can become costly. By doing a little research you can find some that work well. I have actually had pretty good success with my Helios 44-2 58mm f/2 lens using an adapter from Bower. This Helios lens is hard to modify but because I wanted to used it for walking around for different landscapes and scenes, I wanted to have infinity focus available to me. This is also true for a Pentax 50mm f/1.4 that I picked up. It is super sharp and I wanted infinity focus, but Pentax lenses are designed with fairly tight tolerances so the lens was not really an option to modify to obtain the focus I wanted.
Lastly, the most brave and daring option is to modify the lens to allow you turn the lens far enough to obtain infinity focus. As mentioned with my Pentax 50mm lens above, this may not be possible for all lenses. It is most likely not an option, although it may be so do some research, if your lens uses and internal focusing mechanism rather than changing physical the length of the lens to focus, the latter being more common on less expensive lenses which are the best ones to try this option on (I wouldn’t do it on a high end lens, but I also probably would not have spent money on a high end lens with a different mount…see below for more). This type of focusing mechanism where the lens screws and unscrews to change the length of the lens is more common and cheaper. Functionally it is essentially that; a screw that you turn to move the elements closer and further apart from eachother to focus the light. To ensure that when you reach the longest extension of the lens, infinity focus, the lens does not actually unscrew from itself, the manufacturer installs what is known as a “stop” (this one has nothing to do with light though). It is a physical piece of metal or plastic on the inner and outer parts of the screw that hit each other preventing the screw from doing turned any further. Without it, you would just unscrew the lens from itself, and likely damage the lens. As an aside, there is also a stop on the other end of focusing ot prevent the screw from over-tightening, but more importantly to prevent elements of the lens from contacting each other by being moved to close together. You should never modify this stop. Other types of lenses with user a set screw as a stop. I have lenses of both types.
Before embarking on modifying a lens, you should do some research. It is quite possible someone else out there has already tried this and could save you a lot of time and headache before you embark on a modification that is either very challenging or not possible. If you do decide to modify your lens, it is also possible someone has already done it and provided step-by-step instructions on some forums out there which will save you some time as well. There are a few different types of modifications, but the two I have encountered are described in brief here (this is not a tutorial on it some I’m not going to go step-by-step on these lenses). The easier of the two lenses, and the one I successfully modified, was my MTO-1100A, which is a Russian-made 1000mm reflex mirror lens. The particularly lens was probably made in the 1960s and is an absolute beast made of metal. It has a set screw, which prevents the outer housing from being unscrewed from the inner part of the lens. It should be noted that you do have to take off some other simple housing parts to access the screw, but not any parts that could affect the function of the lens. Once you get to the screw, you just loosen it, and physically turn the focusing ring hard enough to have it move a little bit further to reach infinity (thankfully there is quite a bit of room before the screw reaches the end of the thread in the design to do this). Before re-assembling the lens, attach it to a camera after the adjustment to confirm you have hit infinity. Then once confirmed, you can retighten the screw and reassemble the outer housing.
The second adjustment I tried on my Helios 44-2 as I was not sure if it used the same set screw as on my MTO. Unfortunately it requires dissembling the lens, including parts that could cause issues if not put back together properly, and it uses a hard metal stop which is order to modify would require cutting away at the stop to adjust the focus. I did not feel that adventurous, so I did not make the adjustment and instead use a correcting adapter with this lens. It is personal choice to see if this type of adjustment is worth it to you. I have had great success with some of my adapters and did not find the effort and risk worth trying, but you may, so do some research and make the choice for yourself.
So now you know about how to adapt lenses, and what I have done for some of my M42 mount lenses to use them successfully on my Nikon camera bodies. But what types of lenses should you consider adapting? You can adapt most lenses, but because of the adapter you may lose some functionality whether it is ability to use autofocus, or the ability to reach infinity focus. As such, I typically stick with 4 rules when picking a lens to adapt. The first rule is, pick a lens because you like the features and would want it even if it came in the camera mount for your particular system. Don’t pick a lens just because you can adapt it, or because it was cheap. My second rule is to do some research on the type of mount to make sure it is possible to adapt the lens to your camera system and what considerations you might need to take into account. The third rule is don’t bother with lenses that have a whole bunch of electronic features, such as autofocus, image stabilization or chips for distance because likely they will not work when using an adapter and because they were designed for a different camera system. I typically stick with older manual focus lenses and focus more on their image quality than newer features.
Lastly, and this may vary depend on you budget and how the lens will be adapted, but don’t spend a ton on the lens. Look for good quality at a low price, and shop used whenever possible. Often times these older lenses are great optically, but because they are older, people are getting rid of them for pretty low prices. If you want a high end lens for your camera, find a lens that is designed for your camera system as often times the reason for the high quality and price are the newer electronic/automatic features in addition to the quality of the glass and construction. You can just ask yourself, if you didn’t have those features and especially if you need to use a correcting adapter or modify the lens, is it still worth the high price. My guess is a pretty strong “no.” If you really want the highest quality and have the budget, just buy the lens made for you camera system as it is much easier as you know it was designed for and will work with your camera. As you could see I spent $20-$50 on most of my older Pentax and Russian-made lenses and they work great optically. They are only that cheap because they are old and the person selling it has no value in it (maybe they stopped taking photos or inherited it from a family member). Plus, by spending less, you may have more of your budget for additional lenses to adapt to expand your toolbox. Again these are my rules when buying lenses to adapt.
Adapting lenses can be simple or a bit more challenging, but if you successfully do it you will have more tools at your fingertips. So far I mostly stick with old M42 mount lenses as I don’t want to go down the path of having a whole bunch of difference adapters for different lenses. There are a ton of great older lenses out there with plenty of quality life left in them. You can make them work with your camera fairly simply and potentially save some money. Go out and find them and capture the world around you.
Before I go on to specifics about adapting the M42 lens to a Nikon body, I am going to re-post the section with a bit of history and details on the M42 and M39 lenses below:
“M42 and M39 Universal Mounts – Although M42 and M39 mounts are different and were used by different companies, I grouped them together because they shared similar properties. The M## designation reflected the metric 42 or 39mm screw thread. Both used a thread pitch of 1mm. T-Mounts (see below) also have a 42mm diameter, however it uses a 0.75mm thread pitch and is not compatible with M42 cameras and vice versa. The M42 mount was first developed by Carl Zeiss back in the 1930s, and was adopted by many European, and particularly Russian camera and lens manufacturers. The M42 standard utilized a 45.46mm registration distance. As I mentioned above in the Pentax section, the Pentax camera company utilized the M42 mount as well. In the United States became known as the Pentax Universal Screw mount. The same occurred with the Praktica camera brand outside the US, however both are M42 universal screw mounts. The M39 screw mount was developed by Leica prior to the development of the Leica R bayonet mount and had a registration of only 28.8mm which is too short for many other cameras. Early Canon cameras used it (but called the J-mount) as did several of the Russian camera brands. The Zenit camera brand adopted the M39 configuration but extended the registration to 45.2mm. There is no visual difference between the mounts with different registration distances, so you must know for which one your particular M39 lens was designed.”
So know you have been refreshed on what an M42 mount is and a bit of the technical details. As you can tell by the description, a 42mm screw is not going to connect with the bayonet style receiving flange on a Nikon body, so an adapter must be used. Not all that surprisingly, the major camera manufacturer’s who also make lenses, do not make adapters to attach a different type of lens on their camera body. They want you to buy the equivalent type of lens from them with their mount. And, that’s a good business practice, but for the consumer and photographer it limits your world to lenses made from just one manufacturer. Now if I were limited to just using Nikon lenses, I would certainly get over it quickly, but knowing that there are some many different brands and types of lenses out there, I don’t want to be limited. For example, I have a Helios 44-2 58mm f/2 lens at home which uses an M42 lens mount. What is so special about it? It’s just a fast, normal prime lens. I could easily get the 50mm f/1.8D from Nikon (and I own that as well). So why would I want to attach this old lens to my new DSLR? Simple. The bokeh on this lens (a term for the quality of the out of focus area in front of and behind the subject that is in focus) has an awesome swirling pattern to it which I really like for some of my more artistic shots. The smooth bokeh on the Nikkor 50mm f/1.8 is great, but it doesn’t have the same effect. As an added bonus, because there are a lot of these old Russian lenses out there no new cameras today that accept M42 lenses, I was able to pick one up for cheap ($20) on Ebay and it is in flawless condition.
But what good is a fantastic lens for $20, if you can’t natively attach it to your camera, and your camera manufacturer doesn’t make an adapter to attach it? This is where general 3rd party manufacturers come in. There a slew of these 3rd party manufacturers who make adapters for just about any lens/camera combination where the connection is possible (for example Canon EOS lenses, due to their diameter, cannot be adapted to a Nikon body so no reputable manufacturer will make this type of adapter). These lens adapters are very simple in nature, being cut from aluminum, and consisting of the female attachment for the lens on one side and the male flange for the camera body on the other. Some manufacturers that are popular are Bower in the U.S. and Kood in the U.K., but there are many out there including some store brands which are just fine for simple adapters. They are usually sold for just a few dollars so if you get one brand and find there is some aspect that you don’t like about it (for example I have one adapter that does not lock into to the camera body properly) then there is not a whole lot lost and you can try another brand. Again, this is for the simple metal adapters (more on what is not a simple adapter in a minute).
Many lens combinations work really well with a simple adapter, for example mounting a Nikon lens on a Canon camera body. As the throat of the lens on the Nikon is smaller than the opening on the Canon there is no issue there. Additionally as the registration distance (for more on this see this post) for Nikon is longer than that for Canon, there is no issue with not being able to focus to infinity, however you may lose a little, but of focusing power on the shorter end. One thing to be weary of is the distance that the lens protrudes into the camera body. If one camera system is designed for a lens where the back element is deep in the body and you attach that lens to body where the system does not require the lens to stick into the body very deeply, you may end up with issues. The most common of these is that the reflex mirror actually hits the end of the lens which can do damage to the lens, but more likely could break the mirror in the camera (not something you want to fix). To avoid this, do your research online and look for groups on photography forums where these are discussed (such as Flickr or Photo.net). A few simple web searches will avoid you a whole lot of hassle before spending money on a lens that may end up breaking your camera.
Nikon, is actually one o the more challenging camera bodies to adapt lens to, but it also one of the safest. How so? First off, the opening or throat diameter on the Nikon body, is fairly narrow. As I mentioned in the earlier posts, Nikon has made very few changes to their mount since it came out in the 1950s and this “narrow” throat is one of the features that has been maintained. Why is this an issue? Most lenses with different mounts will still work as the throat is very similar to that of the Nikon. However some manufacturers, Canon with their EOS mount being the most recognizable of these brands, have a throat opening which is much wider than that of Nikon. As such, the end of the lens is too large to fit into the throat on a Nikon body. This is great for Canon users as they can use their Canon lenses and also use the narrower Nikon lenses which will mount deep enough in the body to make up the difference in registration distance with just a simple adapter. However, as you may be able ot tell from the other direction, Nikon users cannot use Canon EOS lenses on their bodies. The physics of it just don’t mix. A very complex adapter with lens elements would need to be developed, and the cost and headache of this type of adapter would not be worth the effort. As such, Nikon users are a little more limited in what lenses they can choose from when venturing outside of their brand. As noted by me, a Nikon user, this is very disappointing as Canon does have some great lenses I would like to try (although not enough to want to switch brands). I do not fault Canon or Nikon for this as it is just a product of the difference in design (at least I’ll be optimistic and say that this was not the intention of making the difference in design larger than any other two brands).
The second challenging part about adapting lenses to Nikon bodies is that the registration distance on a Nikon is 46.5mm and is longer than most other major camera manufacturers. By putting a lens on that is designed for a system with a shorter distance, you can be certain that you will not run into issues with the mirror hitting the lens. However, on the other side as the lenses were designed with a shorter registration distance in mind, you may actually lose the ability to focus to infinity (the lens is physically further away from the sensor and the stop that the manufacturer puts in the lens at infinity, will not allow the lens to be focused far enough to make up for that difference. This is exactly the issue of adapting my M42 lenses to my Nikon bodies. There are three main options when you run into this situation. You can use the lens as-is with a simple adapter without being able to focus to infinity, you can use a more complex adapter that uses an optical element to correct for the distance and allow for infinity focusing, or you can modify the stop in the lens to achieve infinity. There are advantages and disadvantages to each of these options. To explore these options, I will let you know what I have done on a few of my lenses.
The main advantage to using a lens as-is is that you do not need to modify any part of the lens, or add additional glass between the lens and the image sensor. By adding in more glass you risk the potential for degrading the quality of the image produced by the lens as every time you pass light through another element, you take this risk. Also, as the adapters are made by 3rd party manufacturers, you risk that the glass used does not have the same quality as the glass in the lens itself. Just as a chain is only as good as its weakest link, a lens is only as good as its worst element. I have a Pentax 50mm f/4 macro lens with an M42 mount, which I picked up for $50 on EBay. It is a fantastic lens with some great bokeh. As it is used for macro work, I use it with a simple adapter and no additional glass element as all of my work involves focusing close and rarely want to use it to focus to infinity. This maintains the optical quality I want for the fine details of macro work while sacrificing a function of the lens that I do not use often for macro work. For this situation this was the best option for me.
The second option is to use an adapter that uses a correcting element to achieve infinity focus. The advantage here is obviously you do not need to modify anything and you can have infinity focus. The drawback is that you are introducing an additional piece of glass between the lens and the sensor. Depending on the adapter you get, this may be just fine, but is also may cause degradation in the image quality of the lens. Often these elements do not have the same quality or coatings as the elements used in the lens. This type of adapter is more expensive than the simple adapters, so going by trial and error as mentioned above can become costly. By doing a little research you can find some that work well. I have actually had pretty good success with my Helios 44-2 58mm f/2 lens using an adapter from Bower. This Helios lens is hard to modify but because I wanted to used it for walking around for different landscapes and scenes, I wanted to have infinity focus available to me. This is also true for a Pentax 50mm f/1.4 that I picked up. It is super sharp and I wanted infinity focus, but Pentax lenses are designed with fairly tight tolerances so the lens was not really an option to modify to obtain the focus I wanted.
Lastly, the most brave and daring option is to modify the lens to allow you turn the lens far enough to obtain infinity focus. As mentioned with my Pentax 50mm lens above, this may not be possible for all lenses. It is most likely not an option, although it may be so do some research, if your lens uses and internal focusing mechanism rather than changing physical the length of the lens to focus, the latter being more common on less expensive lenses which are the best ones to try this option on (I wouldn’t do it on a high end lens, but I also probably would not have spent money on a high end lens with a different mount…see below for more). This type of focusing mechanism where the lens screws and unscrews to change the length of the lens is more common and cheaper. Functionally it is essentially that; a screw that you turn to move the elements closer and further apart from eachother to focus the light. To ensure that when you reach the longest extension of the lens, infinity focus, the lens does not actually unscrew from itself, the manufacturer installs what is known as a “stop” (this one has nothing to do with light though). It is a physical piece of metal or plastic on the inner and outer parts of the screw that hit each other preventing the screw from doing turned any further. Without it, you would just unscrew the lens from itself, and likely damage the lens. As an aside, there is also a stop on the other end of focusing ot prevent the screw from over-tightening, but more importantly to prevent elements of the lens from contacting each other by being moved to close together. You should never modify this stop. Other types of lenses with user a set screw as a stop. I have lenses of both types.
Before embarking on modifying a lens, you should do some research. It is quite possible someone else out there has already tried this and could save you a lot of time and headache before you embark on a modification that is either very challenging or not possible. If you do decide to modify your lens, it is also possible someone has already done it and provided step-by-step instructions on some forums out there which will save you some time as well. There are a few different types of modifications, but the two I have encountered are described in brief here (this is not a tutorial on it some I’m not going to go step-by-step on these lenses). The easier of the two lenses, and the one I successfully modified, was my MTO-1100A, which is a Russian-made 1000mm reflex mirror lens. The particularly lens was probably made in the 1960s and is an absolute beast made of metal. It has a set screw, which prevents the outer housing from being unscrewed from the inner part of the lens. It should be noted that you do have to take off some other simple housing parts to access the screw, but not any parts that could affect the function of the lens. Once you get to the screw, you just loosen it, and physically turn the focusing ring hard enough to have it move a little bit further to reach infinity (thankfully there is quite a bit of room before the screw reaches the end of the thread in the design to do this). Before re-assembling the lens, attach it to a camera after the adjustment to confirm you have hit infinity. Then once confirmed, you can retighten the screw and reassemble the outer housing.
The second adjustment I tried on my Helios 44-2 as I was not sure if it used the same set screw as on my MTO. Unfortunately it requires dissembling the lens, including parts that could cause issues if not put back together properly, and it uses a hard metal stop which is order to modify would require cutting away at the stop to adjust the focus. I did not feel that adventurous, so I did not make the adjustment and instead use a correcting adapter with this lens. It is personal choice to see if this type of adjustment is worth it to you. I have had great success with some of my adapters and did not find the effort and risk worth trying, but you may, so do some research and make the choice for yourself.
So now you know about how to adapt lenses, and what I have done for some of my M42 mount lenses to use them successfully on my Nikon camera bodies. But what types of lenses should you consider adapting? You can adapt most lenses, but because of the adapter you may lose some functionality whether it is ability to use autofocus, or the ability to reach infinity focus. As such, I typically stick with 4 rules when picking a lens to adapt. The first rule is, pick a lens because you like the features and would want it even if it came in the camera mount for your particular system. Don’t pick a lens just because you can adapt it, or because it was cheap. My second rule is to do some research on the type of mount to make sure it is possible to adapt the lens to your camera system and what considerations you might need to take into account. The third rule is don’t bother with lenses that have a whole bunch of electronic features, such as autofocus, image stabilization or chips for distance because likely they will not work when using an adapter and because they were designed for a different camera system. I typically stick with older manual focus lenses and focus more on their image quality than newer features.
Lastly, and this may vary depend on you budget and how the lens will be adapted, but don’t spend a ton on the lens. Look for good quality at a low price, and shop used whenever possible. Often times these older lenses are great optically, but because they are older, people are getting rid of them for pretty low prices. If you want a high end lens for your camera, find a lens that is designed for your camera system as often times the reason for the high quality and price are the newer electronic/automatic features in addition to the quality of the glass and construction. You can just ask yourself, if you didn’t have those features and especially if you need to use a correcting adapter or modify the lens, is it still worth the high price. My guess is a pretty strong “no.” If you really want the highest quality and have the budget, just buy the lens made for you camera system as it is much easier as you know it was designed for and will work with your camera. As you could see I spent $20-$50 on most of my older Pentax and Russian-made lenses and they work great optically. They are only that cheap because they are old and the person selling it has no value in it (maybe they stopped taking photos or inherited it from a family member). Plus, by spending less, you may have more of your budget for additional lenses to adapt to expand your toolbox. Again these are my rules when buying lenses to adapt.
Adapting lenses can be simple or a bit more challenging, but if you successfully do it you will have more tools at your fingertips. So far I mostly stick with old M42 mount lenses as I don’t want to go down the path of having a whole bunch of difference adapters for different lenses. There are a ton of great older lenses out there with plenty of quality life left in them. You can make them work with your camera fairly simply and potentially save some money. Go out and find them and capture the world around you.
Monday, June 20, 2011
Not Enough Time In the Days
Unfortunately there was not enough time this week to do justice to a post and therefore I will not be posting this week. I will make up for it in the coming weeks and post with an extra post. Stay tuned...
-Adam
-Adam
Monday, June 13, 2011
Focal Lengths, Part I: Wide-Eyed – Capturing the World with Wide Angle Lenses
In recent weeks I’ve been trying to tie the posts on this blog to techniques, or equipment I have recently used in my 365 Challenge. This week is no different. However it is also the first in a series of short posts discussing a specific range of focal lengths of lenses. In these posts I’ll talk about the lenses themselves, challenges with working with them, and touch briefly only techniques for using them effectively. The series likely with not be posted in consecutive weeks, but I’ll be sure to hit the three major groups: wide-angle, normal, and telephoto. This week is all of about wide-angle lenses.
In a previous post on zoom and primes lenses a touched briefly on focal lengths and how they are determined. I’m not going to repeat that all again here, but please check it out in the other post if you want more info. What I will do is define the major ranges of focal lengths, starting with normal lenses. Normal, as accepted by photographers and lens manufacturers refers to lenses with focal lengths around that of 50mm on a 35mm frame. Normal lenses ultimately range from about 35mm up to around 75mm. The notable feature is that lenses in this range produce images approximate to human vision. In actuality the range is not defined by human vision but actually by the relationship to the diagonal measurement of the film or digital frame. On a 35mm frame, the diagonal measure around 43-44mm, but for ease of definition is was agreed to make the standard length 50 mm on this frame size. It should be also noted the remaining ranges are all based on a 35 mm frame size. For cameras with a smaller or larger frame size, crop factors should be used to compare the ranges (check out this post for the reason why). Here are the ranges for the 6 focal length ranges as commonly accepted by photographers, although these may vary slightly.
Lens Range | Focal Length (35 mm frame) | Focal Length (1.5x Crop Sensor) |
Ultra-Wide Angle | < 20 mm | < 14mm |
Wide Angle | 20mm - 35mm | 14mm – 24mm |
Normal | 35mm – 70mm | 24mm - 47mm |
Short Telephoto | 70mm – 105mm | 47mm - 70mm |
Telephoto | 105mm – 300mm | 70mm – 200mm |
Super Telephoto | > 300mm | > 200mm |
As stated early on, this post will focus on the wide and ultra-wide angle ranges. Lenses in these ranges allow you to capture an image with an angle of view that is wider than normal human vision. As such there are both technical and artistic advantages to using a wide angle lens. Wide angle lenses can have an effect on images by distorting the perception of depth. A shot taken of two objects that are not in the same plane from the camera using a normal lens with roughly reproduce the perception of depth between the objects as witnessed by looking at them. However when using a wide angle lens, the perception of depth is distorted so the objects look further away from each other than they are in real life. This distortion can be used both practically and artistically. By getting up close to a subject with a wide angle lens, you can make the subject stand out from the background. The near subject will look very near and much larger than subjects in the background. Conversely, subjects further away from the lens will look very far away and smaller. When shooting with a wide angle lens, it increases the focus on the near subject. This effect can also be used to deceive the viewer intentionally be changing the proportions of the subjects. While used artistically can have the effect described above. However, it can also be used intentionally by altering the perceived spatial relationships of the viewer. This technique is often used by real estate agents when taking photographs of the interior views of a structure (house, building, etc). This effect can make the rooms look larger than they are in real life. While this may be seen as deceiving (and trust me the realtors know they are doing this), it also allows the photograph to capture more of the space with a single photo and can give a better idea of the space than one shot with a normal lens.
On the same note, the use of a wide angle lens can also allow the photographer to capture more of a scene than would otherwise be possible. For example, when shooting a large group of people, a photographer may opt to use a wide angle lens to capture everyone without having to position themselves very far away from the group (or maybe there is not space to be that far away). This can be a real advantage. Landscape photographers also tend to use wide angle lenses to be able accentuate the vastness of a scene. For example a shot of the Grand Canyon would have more impact when taken with a wide angle lens rather than a normal lens as it intentionally makes the scene look even bigger than it already is resulting in a greater impact.
Using a wide angle lens has some considerations that need to be accounted for by the photographer. First off, as pointed out above, a wide angle lens distorts the perception of distance in a photograph. It also distorts the perception of the depth of field, or the area in front of and behind the subject that is considered to be in acceptable focus. As a result, the use of a wide aperture has a less dramatic effect with a wide angle lens as it does with a normal or telephoto lens. This is not just a negative, but a positive effect as well. It potentially allows the photographer to take a photo using a wider aperture, allowing in more light, with less of an effect on the depth of field. This can be very useful. Additionally, a wide angle lens captures more light than lenses of longer focal lengths as it is collecting the light from a much larger angle. As such, cameras with wide angle lenses can usually be hand held a slower shutter speeds than those of greater length. Also, wide angle lenses, due to the nature of the short focal length, tend to be physically shorter as well (not always true, but often). The shorter length lessens the effect of handshake from the photographer. The “Sunny 16 Rule” is a standard that all photographers should know. It states that at f/16 on sunny day, the slowest shutter speed that can be handheld is 1 over the focal length of the lens. For a normal 50mm lens, this would be 1/50th of a second (why the most commonly used shutter speed acknowledged for handholding is 1/60th of a second). That means for telephoto lens of 200mm focal length, the slowest shutter speed for hand holding would be 1/200th of a second. On the side relating to wide angle lenses, a 20mm lens could potentially be handheld at 1/20th of a second. This rule is no exact as it also depends on the steadiness of the hands of the photographer, but it is a good approximation.
An additional consideration is a negative of wide angle lenses (although can be used artistically). Wide angle lens tends to distort the view of straight lines in an image. Although considered rectilinear, meaning that the lens should make straight lines look straight, distortion can still be apparent when using wide angle lenses. Manufacturers go to great pains to correct this distortion in the design of the lens. However, in ultra-wide angle lenses, the distortion can still be present. This type of distortion is known as barrel distortion as it causes straight lines to bow out towards the sides of the frame like the shape of a barrel. This effect is often minimal in the center of the image, but can become predominant at the edges of the frame. Thankfully, many of the popular post-processing software can easily correct this type of distortion, but if you happen to still work with film, this is a big consideration when shooting.
Lastly, most filters can be used on a wide angle lens, but there are a few exceptions. The first exception is with the use of polarized filters. Due to the polarization of light by the filter and the angle of view, polarized filters can cause problems when shooting (the polarization can causes darkness and patterns around the edge of the frame). The second exception is with the use of ultra-wide angle lenses. In the ultra-wide range, the metal ring used on circular filters, or the filter holders for square filters, can often be seen in the view of the lens. To get rid of this you would need to crop the photo which reduces the effective benefit of using an ultra-wide angle lens. Thankfully filter manufacturers make low profile circular filters and low profile holders for square filters, however if you lens is really wide it may not matter. I happen to use Tiffen’s wide angle filters and have no major issues when using my 10-24mm zoom lens at 10mm (15mm on a 35mm frame). Any wider though and I would not be able to use a filter on my lens. The last exception is also with ultra-wide lenses. Due to the design of lenses at the very short focal lengths to allow for a very wide angle of view (approaching 180 degrees), often the front element of the lens can actually be convex in shape. One example of this is the 8-16mm lens from Tokina. This causes issues when trying to attach a flat filter on the front of the lens. Be sure to read up on your lens before buying filters (or even the lens if you want one that you can use filters with).
That’s it for this week. I am trying to keep these ones shorter as some of my past posts have been very long. Using wide angle lenses can be great both artistically and for practical purposes. Thankfully many of the lenses that come with entry level and mid-level DSLRs usually encompass part of the wide-angle range (Nikon’s usually start at 18mm). This can allow you to test out using the range before investing in a dedicated wide angle prime or zoom lens. Like any of your lenses, you should practice using them and you will get the hang of it. As always, get out and shoot.
Subscribe to:
Posts (Atom)