>> The human eye features two systems for adapting to light levels. One 
>> is the iris, which can adjust the amount of light that enters the eye. 
>> But in really low-light conditions, a second set of light receptors in 
>> the retina which respond to much lower light levels. (And don't 
>> distinguish colour. That's why in the dark, everything seens monochrome.)
> 
> Yes. But, interestingly because of the chemistry of the eyes, it takes 
> quite a while before night vision is effective.

More precisely, because the photosensitive chemicals used for low-light 
vision get utterly saturated under normal lighting conditions, and once 
they are depleted, it takes a while to manufacture more. (Under 
low-light conditions, it gets depleted so slowly that the speed of 
manufacture isn't an issue.)

Yeah, it could possibly be improved. But given that homo sapiens is not 
a nocturnal species, the fact that we can see in the dark at all is 
fairly impressive. *Realy* nocturnal animals like cats have a wide range 
of special adaptations for low-light conditions...

>> Likewise. I can also adjust the convergence...
> 
> So can I. As a teenager I got swept up in the whole stereogram thing.

I only caught on once I finally figured out how they're actually 
supposed to work. The whole "look into it, not at it" thing didn't make 
any sense to me. When I finally realised they meant your eyes are 
supposed to hyperconverge, it suddenly made much more sense.

And now I draw my own using Notepad...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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