neutral reference scale?
neutral reference scale?
- Subject: neutral reference scale?
- From: Roberto Michelena <email@hidden>
- Date: Wed, 28 Mar 2001 22:34:42 -0500
I would like to find something like a gray step wedge, that could be
purchased somewhere, and can serve as a visual reference of absolute
neutral gray. I mean something like a=b=0 if measured with a
superexpensive instrument under any daylight-kind (D50, D65, etc.)
illumination.
Is there such a beast for under $50 anywhere?
The idea is that the damn spectros are so unable to deal with many of
today's papers and inks, that you'll better resort to your eyes again.
How? well, you make a profile the normal way. Then you print a ramp that
goes from L=100 to L=0, absolute colorimetric.
It won't be neutral. But being absolute, it should.
As a first correction, you edit the paper color to what you believe it
should be.
You print again. Obviously, it's still not neutral. What's more, the cast
is not constant through the ramp.
So you pull your magic "neutral reference ramp", and for each patch of
your printed ramp you find an equivalent lightness patch on your
reference ramp. We're not linearizing lightness here, after all. Then you
see what the cast is, since you've got a neutral at the side. And for
each patch, you can note the needed correction ("less magenta", "more
yellow", etc.)
Then you apply those to the profile, in an appropiate software;
ColorBlind Edit, Kodak ColorFlow Profile Editor, etc; PrintOpen 4 (PC)
lets you modify the neutral gray composition. I wonder if it pulls the
whole profile around it; it probably should.
Once you have a real neutral skeleton (or more properly said, a vertebral
column) any profile edits are far more workable.
So, again, does anyone know of such a "neutral ramp reference"? might I
assume that the black component in something like a Matchprint base is
neutral? or photographic b&w paper? etc.
-- Roberto Michelena
EOS S.A.
Lima, Peru