Ann Sanfedele <[EMAIL PROTECTED]> wrote: >Mark Roberts wrote:
>> Look at it this way: Yellow light has a wavelength around 575 nm. >> Combining red (650 nm) and green (500 nm) *doesn't* produce light of 575 >> nm wavelength - you just have two separate wavelengths present at the >> same time - but it'll *look* the same as light of 575 nm wavelength to >> the human eye. Cool, huh? > >Very cool :) But something puzzles me. This all sounds like things that >apply to images on a monitor or stage lighting, for instance, but once you >have a hard copy of something, you are dealing with pigment, yes? You're dealing with 4 pigments; cyan, yellow, magenta and black. The cyan pigment reflects certain wavelengths and absorbs certain wavelengths. Likewise, the yellow pigment reflects certain wavelengths and absorbs certain wavelengths. When both cyan and yellow pigments are present, there'll be two different sets of wavelengths reflected and your eyes will perceive the result as red. >Given I have a piece of red cloth that is the same color as a piece of matte >paper I've printed (and the same reflective um "index") >they look the same in the same light to the (same) human eye. When both cyan and yellow pigments are present, there'll be two different sets of wavelengths reflected and your eyes will perceive the result as red. Your red cloth is probably dyed with something that just reflects red light so it'll be reflecting one wavelength (to simplify slightly - it's probably reflecting dozens with just one dominating) - it won't be the same wavelength as either the cyan *or* yellow pigments in your print, but your eyes will see it as the same color. >umm so the pigments have different reflective qualities that react to light >differently? It's possible. -- Mark Roberts Photography and writing www.robertstech.com
