Graphics Programs Reference
In-Depth Information
sent the U.S. Web Coated (SWOP) v2 data directly to the
Euroscale Coated v2 press
without
converting the data for the
SWOP process.
The question then becomes, how bad does the image look with the
Pre-
serve Color Numbers
check box on? In some cases, the color appear-
ance might be fine and require only some minor editing of the document.
If this appears to be the case, you would assign the Euroscale Coated v2
profile to the document using the
Assign Profile
command, which
would produce the same color appearance, and tag the image as you
intend to handle it. In this case, the color appearance with
Preserve
Color Numbers
isn't too bad. The image appears a bit warmer and a bit
brighter but not terribly so. The alternative is that you could conduct a
CMYK-to-CMYK conversion, in this case from U.S. Web Coated (SWOP)
v2 into Euroscale Coated v2. This process may or may not work well
depending on whether the two flavors of CMYK are similar or not.
The downside is that some changes are bound to occur in the black
generation.
Some CMYK to CMYK conversions are just not going to work well.
For example, if the original CMYK document was separated for newsprint
and needs to be printed on coated paper, it will be far better to convert
from Newsprint CMYK back to RGB, edit to produce the best possible
color appearance, and then convert from RGB back to CMYK using a
more appropriate black generation for the coated press. CMYK to CMYK
can also present a big problem if this conversion has to take place on
images that contain very pure black elements like drop shadows or even
text. Those elements may have been created originally using just the
black channel to define this pure black, yet after a CMYK-to-CMYK con-
version, these elements usually will be reseparated into a mix of CMY
and K channels. This will be less an issue if the text was created in RGB
in Photoshop, but text created in a page layout application likely will be
separated in such a way that it is fully separated on just a black channel.
Converting 8-bit CMYK to LAB and back to CMYK isn't necessary and
due to the issues surrounding 8-bit files into and out of LAB can cause
banding and data loss. Although this technique has some supporters, I
feel its far less damaging to convert CMYK back to a well-behaved RGB
working space and then convert that RGB data to CMYK.
