Since I got a reply from you (in additional to the copy to the list), I
assumed you are responding to my earlier message? The reply doesn't seem to
be related though since I didn't talk about calibration. Maybe you read a few
messages and then responded to all of them when you reached mine?
<< You are right for traditional printing, but you just can't calibrate gum
printing accurately. I don't think you can even calibrate it
inaccurately - it has a mind of it's own. Most folks are thrilled if
they can develop some consistency.
I didn't know she was going to do gum printing. For some reason I missed the
original message and only read from the responses.
>> The calibrated scans are calibrated for an offset press.
Yes. Your knowledge in color calibration is amazing. Just by your one line, I
believe your knowledge exceeds all one can reads about color calibration in
all magazine articles currently available. All those articles that I have
read, I think the writers don't know anything about calibration at all. They
just copied and recopied the same information again and again.
>> If you want accuracy in 3 color gum (a dubious goal at best) you must
develop your own color corrections anyway. The ones in a calibrated scan
will have
the curves set incorrectly, so why pay extra for someone to do it wrong?
>>
Yes, and it is not an easy job. To take care of the imperfection of dye (or
pigments in this case), some correction must be made. This *cannot* be done
by just adjusting the curves on the color channel because the basic problem
is not adjust the curve for any color channel but to adjust one color
information when another color is present (e.g.: reduce yellow when red is to
be printed because the "magenta" used already contained yellow, instead of
just reducing yellow).
For pigment printing it is even more complicated because pigments are not
truly transparent. Even those categorized as transparent pigments are
semi-opaque compared to dyes.
I have developed custom color correction filters (in Photoshop and standalone
software) some film recorder - negative combination. About 125 color patches
were read and then a mathematical model is built. First-order correction
gives very good result compared to the uncorrected scan. Second-order
correction is even better, but it takes longer to run, but for that
particular application, time is not a big concern, so it worked very well!
Sorry to go off-topic again! :P :)