Photographic Optics and Human Vision
/Photographic Optics and Human Vision
January 8, 2015
I left New York early September, 2014 with the intention of screenwriting in Asia but photography and cultural studies ended up my main focus. On the other side of the earth I found everything around me to be just way too interesting to retreat to an inner world. If you want to write a screenplay hole up in a hotel room, don't go to a country you've never been to before. The things you learn on the road! I was in Japan and Korea from 1999-2000 and unfortunately was unable to get back to this part of the world until almost 15 years later. As of this writing, I've spent two months in China, two in Southeast Asia visiting Thailand, Laos, Cambodia, Vietnam, Malaysia, and Singapore, and am now in India until I return to New York end of February. I've been wanting to explore these countries my whole life so the only way to really do it the way I wanted to was to just commit to a lengthy block of time. While six months seems like quite awhile, I've found it to be not nearly enough. Enough to get a good taste of it but that's about it.
The regional diversity of this continent is staggering and thus incredibly visually inspiring. India, where I am now, is in my opinion the crown jewel of this. Despite some common threads, every sovereign state here couldn't be more different from one another, nevermind the countries within countries that define this part of the world. Surrounded by such natural and cultural beauty, I've found it difficult to put the camera down. The other side of it though is widespread, tragic poverty and I've seen things here that have completely transformed my perspective. I think coming to the other side of the world not only is a wonderful opportunity to explore the cultures of billions of others but also makes you acutely aware of your own and the values that define it. If as a westerner you have these experiences and remain unfazed by them then your fashionable armor of cynicism is truly impenetrable.
I've forced myself into the discipline of shooting with only four Leica prime lenses. A very wide 21mm Super Elmar f/3.4, the standard street shooting lenses 35mm Summicron f/2 and 50mm Summicron f/2, and a very long 90mm Summarit f/2.5. The goal I've arrived at for these images is Naturalism and in trying to achieve this I've come to many conclusions about how the recreation of human vision is affected by various photographic optics.
The Leica 21mm Super Elmar f/3.4 is my newest addition and has been a bit of a revelation. This lens is very light and compact for a 21mm and is the closest analog to human binocular vision I've found. Standing there looking at a scene with two eyes open, this lens does a remarkable job of reproducing what you see. This has everything to do with the lack of exaggerated perspective, barrel distortion, and chromatic aberration in this Super Elmar which is the problem I've had with most other 21mm lenses where there is so much edge distortion that only the center of the image is useable. By cropping in so much you're defeating the whole point of using such a wide optic.
I just started shooting in India so these aren't necessarily the best images I'll get here but are good examples of what I'm talking about. They were all shot with a Sony A7R which is my preferred daytime camera. At night, the A7S comes out. I didn't do any cropping on these to illustrate the actual Field of View of the lenses. The new version of Lightroom has profiles for every lens Leica makes and it's amazing how effective they are removing any remaining unfavorable optical characteristics.
On any other 21mm lens you would never be able to get this close to a subject without really warping the perspective. The 21mm Super Elmar is amazing.
For comparison, here are a few uncorrected images right out of the Sony A7R shot with a Voigtlander 21mm Color Skopar f/4. As is evident in about 30% of the image, this is not a high quality optic. Fortunately this camera outputs a very robust file and many of these issues are correctable but it's a time consuming process.
The Leica 35mm Summicron f/2 is the king of 35mm manual focus lenses and is in my opinion, better than the more expensive 35mm Summilux f/1.4 as it's noticeably sharper, has cleaner optical separation aka Depth of Field, and is quite a bit lighter. I would compare any 35mm lens in Full Frame format to human monocular vision, that is what you see looking at a scene with one eye closed. The 35mm is widely considered to be a "Normal" optic for a Full Frame imager; one that does not create photographic distortion or magnification like wide angle and telephoto lenses do. Technically, a 40mm would be the Normal lens for the Full Frame format as the the diagonal of the 24x36mm imager measures 43.3mm. 35mm is quite close to this as is 50mm so these lenses are both considered Normal or "Medium" focal length as supposedly they, "reproduce a Field of View that generally looks "natural" to a human observer under normal viewing conditions."
In my opinion this notion is worthy of reconsideration as it's true but it only accounts for how we see with one eye which does make sense for a single optic and single imager. It does not take into account the fact that our vision is binocular and the Field of View our brains resolve is actually far wider than either a 35mm or 50mm lens reproduces. As I mentioned, I've found the 21mm Super Elmar to come very close to what we see with both eyes open even though we're actually seeing even a touch wider, more like a 18mm. Some of this extended field is in our peripheral vision though which is not fully processed by our brains and the distortion found on most lenses wider than 21mm mitigates any real authentic increase in Field of View. In practice, a 24mm or 28mm is also a good choice but if the optical quality of the lens isn't there, what you photograph will not be a good reproduction of what you actually see with your own eyes.
The 35mm lens is still a relatively wide Field of View, reproducing most of what we would see with our binocular vision but attractive optical separation is also possible because this lens is actually very slightly telephoto. This is why it's the preferred optic for street and docu photography; the context of the subject is nicely reproduced but the depth of the scene is well defined by separation.
Though not the first choice of most photographers for a portrait lens, I love shooting them on a 35mm if you're able to get close enough because it creates an image with both a lot of context and very pretty depth of field.
The way I'm shooting these days, I'm not using a 50mm lens for much more than portraits. This lens while considered to be close to a "normal" size is in my opinion, actually very telephoto. You still get the context but the subject is significantly separated from it which makes it perfect for capturing a lovely close up from a distance. The Leica 50mm Summicron is tack sharp but because the the focus is so much more selective, getting the image in focus quickly and accurately can be quite difficult.
Any lens longer than a 50mm really starts to flatten things out too much in my opinion. You don't get an accurate sense of depth in the scene anymore. This is obviously useful for digging out subjects from a distance or for a particular artistic effect. Setting up a long lens shot in street photography can be quite difficult as you have zero control over your subject. I prefer to just get close with a 35mm, 28mm, 24mm, or even 21mm. I actually love shooting people with the 21 as it forces me to get closer than I ordinarily would which means discretion and sensitivity become even more crucial.
Here are a few examples from the Leica 90mm Summarit f/2.5. Do your eyes see like this? Mine don't! The truth is, very long telephoto lenses as beautiful as they can be employ an optical trick so will never reproduce an image that is a faithful analog of your vision.
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