Digital BW, The Print

I thought it was a very good response to your post, Carlis. He explained
the metamerism problem very well, which is what you were asking for.

Steve  

"carlislematthew " wrote:
> 
> Good information - thanks.
> 
> >
> > Peaky spectra **IS** what causes metamerism, regardless of whether
> > you're talking about inks or paint chips or geology minerals! The
> > physics and perceptual science of metamerism is not in question.
> >
> > The cones in your retina have three very broad and overlapping
> > sensitivity curves, but all three centered in the middle (430, 530,
> > 560 nm)  However real-world pigments and light sources often have
> > sharp peaks and valleys and their peaks are often higher or lower
> > than the cones' peak sensitivity.  If the reflectance spectrum of a
> > pigment and the emission spectrum of light source both have, say
> > sharp peaks at 680 nm and 540 nm the resulting color will look
> > yellow.  Shift the peak of the emission spectrum to, say, 500 nm
> and
> > the light will look only a LITTLE different to the eye, but the
> > pigment will look red.
> >
> > > Does this really mean that the yellow ink goes magenta in
> > > tungsten light and green in daylight?
> >
> > No one is proposing that the yellow ink changes color, and if
> you're
> > a "scientist by nature" you wouldn't ask such a question.    The
> > color you see is a result of the COMBINATION of wavelengths hitting
> > your retina.   So If you have equal amounts of red, green, and blue
> > hitting your retina you see white (or grey).    Remove (or reduce)
> > the yellow because its reflectance peak(s) don't line up with the
> > emission spectrum and the result is that cones with the middle
> > spectral sensitivity (530) nm don't receive as much stimulation so
> > your eye sees a different color.
> 
> A scientist by nature is someone that questions, wants to know how
> things work, applies logical thinking to problems and so on.  i.e.
> not someone who knows everything about color, pigments and the eye.
> 
> In my short time on this forum I've noticed you rub a lot of people
> up the wrong way during your many posts.  I think you need to relax a
> little bit and get less enjoyment out of harshly correcting people
> and knowing more than others on a particular subject.
> 
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