Digital BW, The Print

Alan Ansell wrote:
> ...the human visual system can only see roughly the  eqiuvalent of  the 16.7 million colours produced by 256\ufffd (3 x the 8-bit channels), ...
>   
What makes you think that?

We use eight bits per channel (RGB) because it fits the (current) 
computer architecture (and makes a smaller memory footprint and smaller 
files), not because it's a good fit with human perception. A closer fit 
to human visual capability would be around 14 bits per channel. Some 
studies apparently have shown that you need a full 16 bits per channel, 
while some showed you could get by with as little as 12 bits per 
channel. In fact, the resolution you need is not the same with each 
channel -- you need more with green than you do with red or blue. But 
from a computer standpoint, you need either eight or 16 bits per 
channel, so if you want to capture it all, you need 16 bits per channel.

If you want to learn more about human perception with the emphasis on 
art, try "Vision and Art: The Biology of Seeing" by Margaret 
Livingstone. I highly recommend it.
--
Bruce Watson