On 1/30/2013 11:49 AM, Chuck Norcutt wrote:
> And not only that, the retinal blind spot of approx 7.5 x 5.5 degrees
is
> automagically filled in by the brain with whatever it thinks should be
> there... kinda like PhotoShop image fill.
Yeh, much PP goings on---and it is totally required. I think I posted
this before regarding Helmhotz's view on the human eye as an optical
instrument. An English translation of his Popular Lectures on
Scientific Subjects was published in NY in 1873. He cited afterimages,
spherical aberration, astigmatism, CA, vitreous opacities, the
physiological blind spots due to the optic nerve head and its
associated retinal vessels, and the less than perfect clarity of the
cornea and lens even when no actual opacities were present:
"Now it is not too much to say that if an optician wanted to sell me an
instrument which had all these defects, I should think myself quite
justified in blaming his carelessness in the strongest terms, and
giving him back his instrument. "
Curiously guess how many blue cones are in the fovea --the area of
sharpest vision ----that's right, ***ZERO**** They are the most
sensitive cones but only consitiute about 2% of the total as the short
wavelenght light focuses much in front due to the expected CA. There
are separate pathways preserved all the back to the visual cortex
and the sharply focused cones are used for resolution and the brain
Photoshop fills in the blue
color where appropriate and does NOT use them for spatial resolution.
Rather cool solution. So nature, like Moose has no issue fixing
things in post rather than up front where it might be too bulky or
expensive to do so.
Mike
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