Digital BW, The Print

Austin,

One further point on this is that we use our B&W vision - from the rods -
for determining detail, edges, movement, etc., and our color vision - from
the cones - merely adds color to the details provided by the B&W vision. I
suppose it is rather like Lab - the luminosity channel provides the detail,
and the a,b channels the color overlay.

Color vision is believed to be a recent evolutionary add-on to the basic
animal B&W vision. Most animals don't possess the color add-on, and do only
see in B&W.

Bob Frost.


----- Original Message ----- 
From: "Austin Franklin" <darkroom@...>
>
> Also, the human eye does not see only in color.  The human eye has two
> spectral systems based on two different types of receptors known as cones
> and rods. The cones are responsible for colour vision but are much less
> sensitive to low light than the rods. In bright light the cones are active
> and the iris is stopped down. This is called photopic vision. When in a
> darkened area, over a short period of time there are other chemical
> adaptations which make the rods become sensitive to light at about a
> 10,000th of the level needed for the cones to work. After this time we see
> much better in the dark but we have very little colour vision. This is
known
> as scotopic vision.  Both are active at any one time...but it's the
> sensitivity of each that changes.