“Physiology of the Eye” — a return to first principles

[Heroique]

All the threads lately about the “subjectivity of art” are, naturally, provoking a lot of frustration and bewilderment, so I thought one about the “physiology of the eye” might provide a settling influence – though I recognize that’s a tall order.

Here are a couple of interesting views from people we know, and I’d enjoy hearing your reactions…

The camera, AA says in The Camera, is “analogous” but not “identical” to the eye, and he then offers a few first principles about how the eye actually works:

“The camera, for example, does not concentrate on the center of its field of view as the eye does, but sees everything within its field with about equal clarity. The eye scans the subject to take it all in, while the camera (usually) records it whole and fixed. Then there is the film, which has a range of sensitivity that is only a fraction of the eye’s. Later steps, development, printing, etc., contribute their own specific characteristics to the final photographic image.”

I’ve also come across the following piece by art critic Robert Hughes who has his own claims about the eye. The following remarks (from The Shock of the New) lead-up to his discussion of Cezanne, but like AA, he wants to establish some first principles about how the biological eye works:

“Look at an object: your eye is never still. It flickers, involuntarily restless, from side to side. Nor is your head still in relation to the object; every movement brings a fractional shift in its position, which results in a miniscule different of aspect. The more you move, the bigger the shifts and differences become. If asked to, the brain can isolate a given view, frozen in time; but its experience of the world outside the eye is more like a mosaic than a perspective set-up, a mosaic of multiple relationships, none of them (as far as vision is concerned) wholly fixed. Any sight is a sum of glimpses.”

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It seems to me that Ansel Adams and Robert Hughes want to make the most simple and objective claims about the physiological eye, before going on with their instructive work – but can one reconcile their claims? One of my initial reactions is that while AA says the eye “scans,” Hughes would “roll his eyes” at the claim that it “concentrates on the center of its field of view.” Just not possible, one might hear him reply. Likewise, AA might be skeptical about all of Hughes’ talk about “mosaics.”

Or, perhaps the correspondence between their views is greater than any difference.

How would you clarify the matter?

[Drew Wiley]

I had huge arguments with my aunt about this. Seems that this kind of thing was a
vogue idea in the 1930's. She was blind in one eye so rolled the good one around to
capture the whole view, so was hardly objective in relating to how ordinary folks see
things. I really believe that at times I grasp a vast number of details all at once, and
it can be a bit spooky. Now I try to relax more and take my time looking. But either
way, it is the view through the groundglass which determines actual composition
and not my initial reaction.

[mdm]

The eye is exactly like a camera, only difference is that what you actually see has first been run through the old super computer between the ears and as a result reflects years of conditioning, learning and many assumptions. Lots of times we see something but we only assume we have seen it, or we see something because we expect to see it, or we heard it or felt it or sensed it, so we see it. And in that respect a blind person sees just as well as you or I. Perhaps a photograph is the only thing a blind person cant see. So in my opinion none of the senses should be considered in isolation.

David

[Greg Miller]

I had huge arguments with my aunt about this. Seems that this kind of thing was a
vogue idea in the 1930's. She was blind in one eye so rolled the good one around to
capture the whole view, so was hardly objective in relating to how ordinary folks see
things. I really believe that at times I grasp a vast number of details all at once, and
it can be a bit spooky. Now I try to relax more and take my time looking. But either
way, it is the view through the groundglass which determines actual composition
and not my initial reaction.

Your Aunt's vision was actually closer to a camera than the rest of us. Most of us have stereo vision, but your Aunt and most of our cameras had/have mono vision.

Beyond that we have to consider the properties of our film and paper. Most color film has dramatically less dynamic range than the human eye, so scenes are rendered with more contrast than we see with the eye.

And then the brain's ability to self color correct (which film does not). And our memory of color is quite poor and also degrades as time since viewing the scene increases. The list goes on and on...

[Heroique]

Yes, stereo visualization often interferes with my pre-visualization.

I close one eye. I am Cyclops.

It’s interesting to note that both AA and Robert Hughes, in their “first principles” of physiology, use only the singular word “eye,” never its plural form. In quite the opposite direction – yet to confirm AA and Hughes – Bob takes one eye, and divides it into two: “The eye itself,” he says, “is really (physiologically) two eyes in one” (post #6).

There’s a frightening consistency going on.

[Mike Anderson]

Yes, stereo visualization often interferes with my pre-visualization.
....

I'm pretty new to photography and I think one of the hardest things to learn is how to imagine (or predict, or visualize) a scene in 2 dimensions.

...Mike

[Leonard Evens]

It is in fact impossible to see anything in the normal sense without your eye scanning the scene. An interesting experiment involves using some sort of apparatus to fix an object so that it moves with your eye. After a short while the object disappears from view.

[Heroique]

An interesting experiment involves using some sort of apparatus to fix an object so that it moves with your eye.

After a short while the object disappears from view.

I wish some of my landscapes had moved w/ my camera.

Then they’d come into view.

[rguinter]

It is in fact impossible to see anything in the normal sense without your eye scanning the scene. An interesting experiment involves using some sort of apparatus to fix an object so that it moves with your eye. After a short while the object disappears from view.

Yes the disappearance is quite interesting indeed. I've heard about the experiment but not participated in it.

Nystagmus and saccadic eye movements are necessary because of the long half life of cis-retinal. The conversion of trans-retinal to the cis- isomer occurs almost instantaneously (in femtoseconds) when it is struck by photons. And this conversion is what initiates a signal in the attached nerve fiber to the brain. But the process of getting back to the trans- state takes much longer when the photons stop coming.

So if one could keep the eye perfectly still with the same image constantly on the same part of the retina... all the receptors constantly receiving photon stimuli would become saturated (i.e., all their trans-retinal would become converted to cis-retinal) and those receptors would cease sending signals to the brain.

Bob G.

[Heroique]

...fix an object so that it moves with your eye. After a short while the object disappears from view.

Yes the disappearance is quite interesting indeed. ...The receptors...would cease sending signals to the brain.

When this happens, what exactly fills-in the place of the “vanished” object?

Would it look like the “blind spot” we all have on the retina?

This is beginning to sound like magicians and rabbits.