Digital BW, The Print

Ken Schuster wrote:

>I wonder if we're all talking about the same thing. My understanding is that
>metamerism and "bronzing" are the same, i.e., a printed image viewed from an
>angle (usually), displays a metallic-like bronze-tone in the darker ink areas,
>creating an almost posterized or negative image in the worst case. 
>
Nope, bronzing is generally from ink overloading and/or ink remaining on 
the surface.. What you describe is bronzing, not metamerism..

>Chromaticity
>(as it explained to me by the Cone Editions lab manager) is when ink reflects
>differing coloration, depending on the viewing light source...
>
Correct..

> the coloration
>usually being crossovers such as magenta or green. 
>
What you are NOW starting to describe is metamerism..

As I understand it, chromaticity is simply the tendency of reflected 
color to vary in accord with the variance in viewing light hue.

Metamerism occurs when the chromaticity of differing color inks behave 
in ways that result in cross-overs or non-proportional color changes at 
points in the reflected light. 

If I view an apple under a blue-white light it looks more blue than 
under a tungsten light. But, since the color changes are relatively 
proportional and crossover free, my mind adjusts  the image in differing 
lighting to accord with the mind's image of a bright red apple.  In a 
non-metameric print, you can take it into differing lighting situations 
and your mind will adjust what it perceives to accord with the hue 
shifts seen in other observed objects.

However, with a neutral print, if I take the print into daylight and it 
looks green, while in roomlight it looks magenta, what has happened is 
that the changes either have crossovers in some portion of the reflected 
spectra or have become widely disproportional, so my mind doesn't and 
can't automatically adjust o keep what I view seemingly perceived with 
the same hue as it had under another light source...

 

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