Re: Subject: photogravures/metamerism
Re: Subject: photogravures/metamerism
- Subject: Re: Subject: photogravures/metamerism
- From: neilB <email@hidden>
- Date: Wed, 24 Oct 2001 17:44:26 +0100
At 9:08 AM -0400 10/23/01, Tom Lianza wrote:
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Hi All
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David Wollmann wrote:
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I must be seeing the effects of
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metamerism because the prints look one way in my viewing
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both, other way under tungsten, fluorescent and still
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different in daylight.
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I have not experienced this with my color prints only these
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monotone gravures, does this sound like metamerism?
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There seems to a consistent misunderstanding about metamerism that seems to
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run through the ink jet industry and then get reinforced by some
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contributers to this group.
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What David is seeing is precisely what Leonardo daVinci recognized in the
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15th century: The color of an object is effected by the color of the objects
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that illuminate it.
quoting Albert Edgar of Applied Science Fiction, inventor of Diital Ice
Cyan dye absorbes red light, not green, and not infrared.
Where does red become infrared? The human eye falls off
gradually as red deepens into infrared. If the cyan dye opens
too soon in the near infrared, then the eye sees that infrared
as red. This makes the cyan dye appear weak under light that is
rich in infrared, such as an incandescent light, and a print
made with that cyan will have reddish grays under infrared rich
light. If you boost the amount of cyan to neutralize gray under
incandescent light, then under light that has no infrared, such
as flourescent, the cyan will be too strong and grays appear
cyanish green.
Too bad they don't offer a cyan dye that overabsorbes
infrared, because it would have a reverse metamerism, making
grays cooler under warm incandescent light, and warmer under
cool lights like flourescent and daylight. Physics does not
preclude such cyans, they exist, but dyes that absorb infrared
are more rare, and will not end up in an ink cartridge unless
someone looks for them specifically.
One way around metamerism is to use 100% undercut on the K, so
cyan does not enter into the reproduction of gray. Maybe this
is what Epson does on the 10000. Just a guess. This "fix"
however has problems as brighter colors that must use cyan will
still shift, and the dots of ink jet dither are stronger with
100% K. Because Epson does not give us artists access to CMYK
directly, we have no control over any of this anyway. Does
Roland?
Metamerisms can happen with other colors too, but the effect
at the edges of infrared produces the strongest problems. It is
responsible for the greenishness of flourescent lights (and
extreme orangishness of incandescent) on film, the "pink violet"
effect when photographing flowers, and black pants turning
orange with some video cameras.
Silver absorbes all colors, including infrared, almost
equally, so Ansel Adams never had this problem. How is the
small gamut ink set doing with metamerism?
Regards
NeilB
- - - - - - - Neil Barstow - Colour Management Consulting - - - - - - -
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