If you had a camera that had the DR of the human eye but only shot one frame every 10 minutes at ISO 100 only and was only manual focus...I've read in a book of a Russian author (not sure if it was translated to English) that human eye has 5-6 stops of DR. And the reason we can see much bigger range of lightness levels is the ability of our eyes to adapt to the rapidly changing environment.
The book's author was a researcher in photography so this statement might be true. Did anyone hear anything like that?
Yes I have that somewhere.
I always was told our eye has a massive DR but not because of the optics but how our brain can dynamically adjust areas of a scene to make blacks brighter and highlights darker. Kinda like dynamic area ISO.
Dynamic range is the total sensitivity range. Just like with a camera and a computer, the eye/brain configuration chooses which range out of the total sensitivity range to "process to". I think our eyes are capable of well more than 5-6 stops on average at any given moment, but I do not believe we can see the entire 25+ stop dynamic range our eyes have all at once. Exactly how much we can see in any one go I can't say, although if I compare my eyes to my 7D, I can definitely see more than 11 stops at a time. My 7D will either clip highlights or block shadows if I try to capture a scene with 12 stops, but my eyes seem to concurrently handle the highlights and shadows of the same scenes just fine.
It is not your eyes, it is your brain that makes adjustments (a lot faster than your eyes) e.g. walk from a pitch black room out through a door into bright sunlight, your eyes don't see the green grass in front of you as they're adjusting, but your brain interpolates based on previous cognitive experience (it knows what green looks like and what grass looks like and further knows that grass = green)
Not entirely. There are changes in chemical response at the rod/cone level as well that start taking effect when you move from areas of differing brightness. Some of those changes are quick (milliseconds to seconds), some take a little time (minutes), and full adjustment to moving into a very bright or very dark area from the opposite can take over an hour. The brain is effectively a biological superresolution processor, it additively picks up "frames" around 500 fps from our eyes (frames is a bad word...its a continual stream of visual information, and no one has really mapped exactly what it is that our brains process yet), and keeps them in somewhat of a "circular buffer" of sorts (although thats really far too simplistic, as our brains permanently store the majority of what goes in...to varying degrees of memorable permanence), so it definitely has a lot more information to work with than simply a single snapshot of the world from our eyes. But it is not purely 100% a "brain thing"...hence my use of the phrase "eye/brain configuration".
The brain part is also something we can influence to a degree, as well. The notion that "the brain" knows what green looks like, or that there are associations between grass and green, is more than simply autonomic. There is a mental, psychological component to such recognition of what we see as well, and through will you can change your
perception of color or other visual information to varying degrees, and the brains visual cortex will respond. Sometimes its a very subconscious thing...the same lawn under the same light may look muted and dull one day, and vibrant and lively the next, depending on your mood or other mental factors. One can choose to see only vibrant color in fall leaves, or choose to "see deeper" and begin realizing far more than just vibrant color...more nuanced color of greater detail and tonality, by choosing to...(You can try it, it is mostly a matter of focus and intent, sometimes you can even expand your visual field to absorb and recognize more information from a much wider field of view than the brain normally does (which is usually in the 2° degree field of view that comprises the most cone-dense central foveal spot of our eyes)). As a photographer, I have tried to train my brain to see what the camera sees, or what I might end up with in Lightroom, as I look through the viewfinder. Reality and what my creative side can "see" are often radically different things, but you can influence your sight to see reality differently. Changing perception, especially trying to train your brain to have different perception in different contexts, can be time consuming...but the point is "prior cognitive experience" is only part of the story.
"Sight" is far more complex than just the brain, or just the eyes. No one single specific thing controls it all, its not purely prior cognitive experience, and its not purely autonomic. There are thousands of chemical cascade reactions taking place every second in the eyes and all over our brains to support visual processing, adaptation to changing luminance, light and shadows included, adjustment according to intent and focus, etc. I wouldn't call the eye the same as a D800 either. The eye is a continuous, streaming, fluid visual processor, where as a camera is explicitly designed to effectively freeze time for a given duration. I would say the only real similarity between the two is simply that they both deal with the visual, use lenses, and have sensors....but beyond that they function in radically different ways for different purposes.
Someday, far off in the future when we have the kind of bandwidth and picoscale sensor fabrication technology that would make a modern DSLR geek's eyeballs pop and brain boil, I foresee a camera sensor that operates more along the lines of human sight: Extremely high resolution, near-perfect quantum efficiency, extremely high sensitivity, excessively high "continuous frame rate" (tens of thousands of frames per second at least), ultra fast image processor that can do similar things to the brain...additively combine hundreds or thousands of individual "frames" from the sensor into a superresolution image that could potentially be larger in pixel dimensions than the sensor itself, and effectively have unlimited dynamic range (or say something around 25 stops...which might as well be unlimited...2048x more range than the D800 has (if that puts it in perspective. ;P). Of course, we would also need 10 stop inks and paper, 16 stop high density (300ppi) computer screens, etc. to actually make effective use of such an eye-wateringly good camera. Ah, the future is going to be so expensive...