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Only 3 colours?

Stephen H. Westin westin*nospam at graphics.cornell.edu
Mon Mar 25 15:09:35 EST 2002

Ian Stirling <root at mauve.demon.co.uk> writes:

> Stephen H. Westin <westin*nospam at graphics.cornell.edu> wrote:
> > 
> > "Neil" <neil_delver at hotmail.com> writes:
> > 
> > <snip>
> > 
> >> The point I want to make is how interesting it is that we experience
> >> those "fundamental looking" colors, which don't "appear" mixed with
> <snip>
> >> Indeed, from that point of view, we really have four primary
> >> colors since yellow doesn't look like it's made of red and green -
> >> we don't call any colors "reddish-green" etc.
> > 
> > But from a mathematical point of view, three dimensions are sufficient
> > to describe normal human color perception, since it all is mediated by
> > three kinds of cones.
> The rods have a significantly different peak than the green peak, IIRC, 
> 520nm, rather than 550nm.
> In normal (scoptic) vision, are the rods totally saturated?

As I recall, they aren't so much saturated most of the time as they
are drowned out.

> Do they contribute at all to scoptic vision?

Not so you'd notice.

> What about the sense of colour?

Not at all.

Really, there are two different vision mechanisms: photopic includes
color, and scotopic doesn't. Not at all. The mesopic is kinda
interesting, as it uses bits of both.

-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.

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