"Warp" wrote:
> Orchid XP v7 <voi### [at] devnull> wrote:
>> That's... interesting. I'm fairly sure I read somewhere that for
>> *greyscale* the human visual system can only distinguish about 16
>> different levels.
>
>  That's unusually easy to prove wrong. How many bars can you count in
> this image? http://warp.povusers.org/images/grayscales.png
>
>  The number you counted is the amount of grayscales you can distinguish
> at least. (The true number is probably at least that times 10 or more.)

While some cells in the eye may be able to distinguish that many colors, 
that doesn't mean that the visual system in the brain can. A lot of 
preprocessing is done in the eyes themselves before the visual data is sent 
to the brain.

For example, the eyes have an edge detecting layer I think, or something 
along those lines. This layer could find all the edges of the bars in your 
image and send information about these edges on to the brain, so that the 
brain can tell how many bars there are. The eyes also send the actual "raw" 
brightness info on to the brain, but this may be in a "low resolution" where 
no more than 16 different shades can be told apart. However, the brain can 
still count all the bars, becuase of the edges detected in the eyes.

I'm not saying it's like that; just that your image doesn't prove anything 
about the amount of gray scales the brain can tell apart. So it really comes 
down to what you mean by "human visual system" - the eyes or the brain.

Rune

Post a reply to this message