Mark Roberts wrote: > 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. > > --
Thanks, Teach! :) ann > > Mark Roberts > Photography and writing > www.robertstech.com
