My day job for the past 20 years or so has been running an offset printing
operation. I prefer that photographers and designers supply all images as close
as possible to the state that they came out of the camera or scanner. If the file has been
cropped or edited in PhotoShop I prefer getting a copy in the native,
unflattened, and unsharpened PhotoShop format so color in layers can be adjusted
separately if necessary. The exception is re sampling, for reasons explained
It makes little sense for a photographer to darken and correct out a
magenta color cast apparent on his monitor, only to have the file arrive at the
printer and have it too dark and green on its monitors which are calibrated to
simulate ink on paper. There will always be a difference between the color of
the monitor of the photographer and the printer but the monitors and proofing
devices at any good printer these days are carefully calibrated to simulate the
appearance of the entire reproduction chain, which typically includes outputting
the file onto hard dot patterns on separate C, Y, M, K (black) films, exposing
plates using the film, and finally printing the dot pattern with a set of
pigmented inks (which can vary significantly from brand to brand) on paper which
can vary greatly in brightness, color, and finish (i.e., gloss, dull, matte) and
absorption / dot gain).
It is possible for a printer to create color compensation profiles for
each paper/ink combination used. We just did this at our shop with the
assistance of Heidelberg Philippines. A standard test pattern is scanned,
imageset, plated, and printed then measured with a photospectrometer. By
comparing the readings on the press sheet with the values on the original, a
table is built by the software which compensates for the gamut of the ink set
and the brightness of the paper. For example, on a very white gloss coated
stock a light ivory tone might reproduce with a 5% yellow and 2% magenta and
yellow dots, however if the same tone is printed on a dull cream stock no dots
at all are needed because the paper is already the desired color. Printing the
5% yellow and 2% magenta and yellow dots on the cream stock will make the
highlights look dull and muddy.
Once the profiles for the various paper/ink combinations are determined
they can be used on a high-end scanner or PhotoShop to change the scanning or
display settings for hue, contrast, and brightness to simulate the color gamut
and contrast of the ink / paper to the extent possible. Reproducing the
same file on the two difference stocks would require two
different output profiles, one for each paper.
If you view a digital camera file on a monitor in PhotoShop calibrated
to an ink/paper ICC profile, colors like bright purples which printing inks
can't reproduce will automatically be dulled-down on the monitor image to the
shade of purple that can be printed. The overall brightness and contrast of the
screen will be lower, simulating the range of reflectances of the press sheet.
What you see on the screen can be, if the calibration is done well, very close
to how the file will look when printed.
Similar calibration can by done with high-end proofers. For example,
each time the color ribbon is changed in an Imation Rainbow dye sublimation
printer the starting points for the calibration must be downloaded from the
Imation web site using the lot number of the ribbon for reference. A detailed
test subject is then printed and used to fine tune the calibration. The same
test target can be imageset and printed on press, with the Rainbow calibration
adjusted as needed to match the printed results.
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