Re: Print Quality

Probably fifteen years ago, I bought a little card with two magenta
looking color chips on it called the Kodak Color Viewing Light
Selector. There's a number on the back that might be a "part" number:
P3-180. Anyway, the way it works is that the two chips look identical
when viewed under a daylight (5000K) light source, but different when
viewed under anything else. They work because one chip has more
metameric properties than the other (see explanation below).

It's really pretty cool. Now, if you've got a darkroom with only one
light source, you don't need a card like this, even with its fancy
name, to know you're not viewing under daylight conditions. But if
you have a mixed light darkroom area, for example mine with tungstens
and also a window, you can walk around with the card until the colors
match and know that that place is 5000K and the "best" place to view
your prints.

ps Even by a window, the card will show whether the light at that
part of the day is 5000K; it might be cooler or warmer of course for
many reasons. Many printers have viewing areas with artificial light
sources that are supposed to replicate "daylight" and this card will
confirm whether they do or not.

>Jonathan Bailey wrote:
>
>>OK. I'll ask.... what is metamorism?? Thanks - JB
>>
>
>
>Metamerism is a non linear, disjunctive, shift in perceived (or
>reflected/measured) color when the ambient lighting temperature
>changes. It's often called a "color shift" but that is an inaccurate
>description.
>
>Now to REALLY explain it... The human eye and mind combination can
>easily accommodate a wide range of lighting "colors" and adjust
>accordingly.. For example, the color (spectrum) of light emitted by
>tungsten lights and by the sun differs significantly. However, if I
>take a red apple from one lighting condition to another, my mind
>easily adjusts for the variance in color of the ambient light and I
>still see the apple as the same red. That's possible because the red
>apple's reflected colors are relatively uniform across the tonal
>range of visible light.
>
>In instances of metamerism something different happens. At
>particular points in the spectral (hue) range, instead of the
>response being smooth and predictable, instead of it remaining in
>sync with the change in ambient light and the response of other
>colors on the print or object viewed, it departs from that linear
>response.
>
>Let's say you are looking at a neutral B&W print under tungsten
>light and one ink used is significantly metameric. You then move
>the print to daylight conditions and it looks greenish. This
>happens because that ink, instead of giving a response in sync with
>the other inks, diverged towards the green hues instead. The
>problem is that if I then compensate in printing and print the image
>to be neutral in daylight, if I move it to tungsten it looks
>magenta...
>
>You can see the problems metamerism brings.. None of the effects
>are positive. So, you want inksets that exhibit as little
>metamerism as possible (pigments tend to be bigger offenders), or
>you can often use a RIP to compensate for the metamerism of one or
>two inks in a set by instructing the rip to avoid using those ink
>colors when printing specific tones where the metamerism is likely
>to be apparent (neutrals and skintones are most susceptible in good
>part because of the human physiological sensitivity to both
>skintones and slight variances from neutral).
>
>I hope that makes it clearer.
>
>
>
>Keith Krebs
>
>"Just some guy," caretaker of the Multiverse's largest EPSON printer
>User Community (highly recommended by Vogon Poets and MegaDodo
>Publications), at:
>http://groups.yahoo.com/group/EPSON_Printers/
>and the Multiverse's largest Canon printer User Community at:
>http://groups.yahoo.com/group/Canon-printers
>"For the rest of you out there, the secret is to bang the rocks together guys"
>
>
>
>
>
>Jonathan Bailey wrote:
>
>>OK. I'll ask.... what is metamorism?? Thanks - JB
>>
>>
>
>Metamerism is a non linear, disjunctive, shift in perceived (or
>reflected/measured) color when the ambient lighting temperature
>changes. It's often called a "color shift" but that is an inaccurate
>description.
>
>Now to REALLY explain it... The human eye and mind combination can
>easily accommodate a wide range of lighting "colors" and adjust
>accordingly.. For example, the color (spectrum) of light emitted by
>tungsten lights and by the sun differs significantly. However, if I
>take a red apple from one lighting condition to another, my mind
>easily adjusts for the variance in color of the ambient light and I
>still see the apple as the same red. That's possible because the red
>apple's reflected colors are relatively uniform across the tonal
>range of visible light.
>
>In instances of metamerism something different happens. At
>particular points in the spectral (hue) range, instead of the
>response being smooth and predictable, instead of it remaining in
>sync with the change in ambient light and the response of other
>colors on the print or object viewed, it departs from that linear
>response.
>
>Let's say you are looking at a neutral B&W print under tungsten
>light and one ink used is significantly metameric. You then move
>the print to daylight conditions and it looks greenish. This
>happens because that ink, instead of giving a response in sync with
>the other inks, diverged towards the green hues instead. The
>problem is that if I then compensate in printing and print the image
>to be neutral in daylight, if I move it to tungsten it looks
>magenta...
>
>You can see the problems metamerism brings.. None of the effects
>are positive. So, you want inksets that exhibit as little
>metamerism as possible (pigments tend to be bigger offenders), or
>you can often use a RIP to compensate for the metamerism of one or
>two inks in a set by instructing the rip to avoid using those ink
>colors when printing specific tones where the metamerism is likely
>to be apparent (neutrals and skintones are most susceptible in good
>part because of the human physiological sensitivity to both
>skintones and slight variances from neutral).
>
>I hope that makes it clearer.
>
>
>
>Keith Krebs
>
>"Just some guy," caretaker of the Multiverse's largest EPSON printer
>User Community (highly recommended by Vogon Poets and MegaDodo
>Publications), at:
><http://groups.yahoo.com/group/EPSON_Printers/>http://groups.yahoo.com/group/EPSON_Printers/
>and the Multiverse's largest Canon printer User Community at:
><http://groups.yahoo.com/group/Canon-printers>http://groups.yahoo.com/group/Canon-printers
>"For the rest of you out there, the secret is to bang the rocks together guys"
>
>