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Beyond Pandora

Beyond simple curiosity, this is Thinking Too Much. If you're interested in philosophy and/or wild theories, you've come to the right place.

Location: Australia

Paddling somewhere between a mad scientist and an organisational artist. Indecisive, inconsistent and often incoherent.

Saturday, July 30, 2005

Orange Eye

(Orig 29 May 05)
Everyone who photographs people knows about the unfortunate 'red-eye' syndrome that spoils the unplanned photograph. I had a lot of this in the last set of photos I took, but I noticed one in particular that has orange eyes rather than the standard red.

While I know a very little about optics from first semester Physics, I can't put my finger on why this would be so.

So I decided to check it out.

After Googling, a microsoft site on red-eye removal/avoidance explains that red-eye is caused by a camera's flash reflecting off the blood vessels at the retina/back of the eye. A more scientific page (found at the site for Imaging Science at the Rochester Institute of Technology), corrects this - it is a reflection of the pink photopigment in the photoreceptors of the retina. (Photoreceptors are "where the light is absorbed and transformed into the electrochemical signals used by the nervous system. This change is called TRANSDUCTION.")

I had fun for a while finding my blind spot on the same page, and I noticed that the description of various parts of the eye gives the index of refraction for both the lens in your eye and your cornea (clear external layer). Refraction is when light bends as it passes from one kind of physical medium (e.g., air) into another (e.g., water).

You've probably seen pictures where light is shone into a glass triangle, and comes out as a rainbow - because blue light bends more than red light. So my theory is that my friend's eye appears orange because when the light bounced off the back of her eye, it was bent and split like in the prism, showing an orange colour rather than red. This would probably only happen when the eye is at an angle to the camera, as my friend's was.

I haven't been able to find anything to support this, except for confirmation that the red eye effect is sometimes orange. I did find out in the process (here) that a cat's eyes will glow green rather than a human red-eye, and this is because cats and some other animals have extra reflective surfaces in their eyes which help them see light when we humans can't.

If anyone has any further light (sorry) to shed on this matter, I'd love to hear it!


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