On Mon, 22 Oct 2007, Charles Henry wrote:
Vision doesn't work exactly like a camera.
Right. Somehow I confused two things. A maximum frequency is only called Nyquist if it involves sampling and aliasing. There are several maximum frequencies that can be computed for the eye for different circumstances, which are in the range of 10 Hz up to less than 100 Hz, but those are due to low-pass effects.
There's no sampling that occurs--the visual signals are more/less continuous except for momentary "refresh" periods brought about by eye motion and nystagmus. I thought about it today, and I'm not entirely sure why it happens (perhaps there is a certain maximum speed which can be perceived--this is equivalent to saying there is a finite bandwidth of motion perception).
Imho this is because we are trained to see "continuous" (slow enough) motion as continuous and sudden motion as sudden. If a change is sufficiently startling, it makes vision snappier. Sudden motion of the eye causes sudden motion of the scenery relative to vision, so it has an effect similar to sudden motion of physical objects themselves.
It would explain why fast-blinking lights are considered to be straining the eye: the eye (or vision system) makes extra effort as a response to high activity in eye cells due to blinking, even as one wants to ignore the blinking.
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