Not sure which post to respond to so I'll start with the original.
If you're trying to match the black in a photo you'll first have to use
an image editor to get the current images RGB black values. Then in
Publisher create a new color with those same RGB values. Don't bother
with Publisher working in CMYK. You really do limit yourself because of
how Publisher works with CMYK. If you have CMYK images that you want to
place that are already color correct then save them as EPS files from
PhotoShop. That way Publisher (Windows GDI) can't screw them up.
Otherwise Publisher will screw them up by going CMYK -> RGB and then
back to CMYK at the printer. And that's just an abomination... Sooooo
having said that you can always use something like 60/40/40/100 CMYK, or
for RGB you would use 0,0,0. This way if the printing company does what
they should they should convert 0,0,0 to their output ICC profile. If
that doesn't happen then the RIP may catch it and convert it to flat
black. Which in this case is not necessarily the desire result. Unless
you're printing a black page. Which even in that case 100k is not
necessarily desireable since you would want 0% device gray (photocopier
black). That way you really only get billed for a black click. Or the
prepress department converts 100k to a mild rich black. I think the
ratio of cyan to magenta and cyan to yellow is 3:2. Magenta and yellow
are tied together in that they must have the same values relative to
cyan to ensure gray balance.
At any rate, never, ever, ever, even if it's to save your life use 100,
100, 100, 100. That's the surest way to make an enemy. Of course since
it's Publisher generally that will come out as 0,0,0 RGB anyways.
Be careful of using device gray on CMYK pages because device gray cannot
overprint CMY(k) (even 0% device gray which looks black). Two different
color spaces that can't really interact with each other. So device gray
*must* knock out CMYK and device N (spot colors). If you really want
something to be black the surest way to do it is to make it 0% device
gray. If you really want something to be "rich black" then add a bit of
CMY underneath the K (called UCR). The opposite would be to remove CMY
from underneath K (GCR).
Many output devices can be configured to add in UCR, GCR or both to
automatically optimize the page for the output device and color
rendering parameters of the RIP. It's a real mess trying to figure out
who's doing what, where, when, why and how. So for digital printing
sometimes it is far easier to provide an RGB PDF and let the RIP handle
it like on Xerox iGen's and HP Indigo presses. One likes GCR, the other
doesn't. Both can do an amount of UCR. But for offset presses and
flexographic you've got to be careful about that because it takes
sooooooooo much communication to work well.
The trick with rich black is that each company has a different rich
black that they "like". They'll print almost anything in an image
though. Which is a bit of a paradox. Why would you knowingly print an
image at 320% for a rich black, 90,65,65,100 for example, but "fix" the
rich black vector objects to be 40,20,0,100? For that matter if you keep
your M,Y plates within the proper ratio to C then in theory you can
print as high/much as you want with K and you won't have a problem with
the under colors turning the rich black blue, red or yellow. Like the
example above, 40,20,0,100. The ratio is out of balance an therefore
very susceptible to "coloring" the rich black by making it too "blue" or
"red".
So to avoid this we use GCR in various amounts to minimize the amount of
CMY needed and a relatively greater amount of black and still achieve a
visually appealing rich black. GCR is good... Very good...
Rich black is a pain in the sass when the art comes from outside. Check
with your printer to see what they want for rich black. If they don't
want yellow in it, then there's a problem with their process. If M & Y
isn't the same an out of proportion with C then there's going to be a
problem on press most likely. It's all got to be in balance or it's hard
to keep the consistency though the run. Which leads to spoilage. A smart
printing company will use an ink optimizer or device link profile that
will convert CMYK to a new CMYK using GCR so that the visual appearance
is maintained but the CMYK values are changed so that black dominates
the separations. This way fluctuations in the manufacturing process
(printing is a manufacturing process after all) are less likely to
affect the art. This is also a good way of preventing a pressman from
"painting on press". Because *you* give them, or the machine, less
ability to affect the color intentionally or unintentionally. Of course
GCR not done well is as bad as anything else because you can seriously
screw up perfectly good art soooooo easily.
Oh, and depending on which ICC profile is being used to convert to CMYK
you can have different ink limits as well as different amounts of GCR
and different limits on the amount of black (length of black plate,
which is independent of GCR).
Clear as mud? If so, reseparate with medium or high GCR an it should be
a bit clearer
Matt Beals
Consultant
Enfocus Certified Trainer
Markzware Recognized Trainer
(425) 582-8554 - Office
(206) 201-2320 - Voicemail
(206) 618-2537 - Mobile
mailto:
[email protected]
Come visit me at:
http://www.automatetheworkflow.com
http://www.mattbeals.com
http://blog.mattbeals.com
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