RE: color perception differences between eyes

>
Roger writes,


> Bob,
>
> Could the difference you note be a function of the types of  
> primaries each
> Wright and Guild used in their apparatus: Wright used monochromatic
> primaries while Guild used wideband primaries? Pretty sure I heard  
> some
> comments to that effect in explaining the differences.

In the last few years, after having questioned hundreds of  
experienced people about what they were seeing, I am beginning to  
suspect that humans don't calibrate to a white point as such.

Chromatic adaptation has so many levels that we are never going to  
understand it entirely. There can be several types going on  
simultaneously. Nevertheless, the more I look at it the more it seems  
to me that the primary range that the eye relies on is not a light  
neutral but rather a lightish warm gray, something on the order of  
75L10a15b. Some really interesting perceptual stuff goes on in that  
range; for one thing, humans appear to see this range as  
significantly darker and more colorful than a spectrophotometer does.

This makes sense from an evolutionary POV. I can't think of any  
reason why it helps survival to be able to distinguish closely  
similar whites from another. In the warm-yellowish gray range,  
however, live a lot of things that we consider good to eat as well as  
a number of others that consider *us* good to eat.  If evolution has  
programmed us to have more acute perception of this range it would  
not be startling.

If true there are a lot of ramifications for color correction,  
sharpening, and profiling. I'm not saying that it is true, but a lot  
of what I am doing is consistent with it being true.

The conventional wisdom is that we adapt to the ambient lighting in  
order to perceive it as neutral. If instead the adaptation is to  
guarantee that a warm gray is seen as a warm gray, one can understand  
how the conventional wisdom became conventional: on casual  
examination, both theories produce about the same result. But it  
might explain the nagging inability to explain differences in  
perceiving white points.

Dan Margulis


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