440
Working for print
CMYK
Printing inks create color in precisely the
opposite way to monitors. Cyan, Magenta
and Yellow inks (with a little Black for the shadows) are
‘subtractive’ colors: you start with a white sheet of paper, and
the more ink you add, the darker the result.
Magenta and yellow added together make red; magenta
and cyan make blue; yellow and cyan make green. When all
the colors are added together, the result is black.
You can see the effect of subtractive color clearly by
creating magenta, yellow and cyan shapes, and setting their
layer mode to Multiply, set against a white background. The
file CMYK.psd in the Chapter 15 folder on the website includes
these three disks of color: as with the RGB file, try moving
them around and changing their opacity, to see how all the
intermediate colors are made.
RGB
Monitors display colors using Red, Green and
Blue light. These are known as ‘additive’ colors,
because the more light you add, the brighter the result: it’s like
shining torches on a sheet of paper in a dark room. You start
with black, and each torch you turn on increases the overall
light level.
Red and green added together make yellow; red and blue
make magenta; blue and green make cyan. When all the colors
are added together, the result is white.
You can see the effect of additive color clearly by creating
red, green and blue shapes, and setting their layer mode to
Screen, set against a black background. The file RGB.psd in the
Chapter 15 folder on the website includes these three disks of
color: try moving them around, and changing their opacity, to
see how all the intermediate colors are made.
P
REPARING IMAGES FOR PRINT MEANS WORKING AT A HIGH RESOLUTION, AS
we’ve seen earlier in this chapter. But it also entails an understanding of the difference
between RGB and CMYK color models.
For most of the time, you’ll work in RGB even if your final output is destined for CMYK. It’s
quicker in operation – the files are three-quarters the size, for one thing, since they have one fewer
channel – the dialogs are frequently more intuitive, and many of Photoshop’s filters simply don’t
work in CMYK. But the RGB color range, known as its ‘gamut’, is far wider than that of CMYK.
Which means there’s a huge range of colors you can create on screen which simply won’t transfer
onto paper.
Even if you’re only printing work out on your own inkjet printer, you need to understand why
some colors print fine, while others don’t.
15
Print and the internet
SHORTCUTS
MAC WIN BOTH
441
HOT TIP
This may all seem
horrendously
awkward, but the
truth is that after
a while you just
get used to which
colors will print
and which won’t.
If either Proof
Colors or Gamut
Warning modes
do flag up out-
of-gamut colors,
then desaturate
them using Hue/
Saturation until
there’s no visible
difference when
you turn Proof
Colors on and off.
If you are doing work for print that will be sent to a magazine, newspaper or other
publication, then work in RGB – and send them your files in RGB. There’s a good reason for this:
creating effective CMYK files isn’t simply a matter of choosing the CMYK Color option from the
Mode menu.
Professional publications will go to great lengths to print test images, comparing them with
the original files, before producing their own custom RGB to CMYK conversion. A lot depends
on the type of paper used, the printing method – sheet-fed or web offset – as well as the specific
printing machine used. If you convert the files to CMYK first, they won’t be able to perform their
custom conversion and the result will look muddy when printed.
When you do have to convert work to CMYK yourself, however, make sure you get as much
advice as possible from your printer first.
A fan of floppy disks (remember them?) held in front of a
colorful computer monitor. Rainbow gradients such as the one
on the screen are easy to make, and they always look bright
and colorful – on screen, at least.
It’s when you try to get them off the screen that the
problems start. The RGB version of this image looks quite
different to the dull CMYK impression printed in this book.
There’s no way of showing the RGB original in print – that’s the
point of this exercise, after all – but you can compare the two
by opening the file RGB Gamut.jpg, which you’ll find in the
Chapter 15 folder on the website.
One way of telling how your images will look when printed
is to turn on Proof Colors mode (Cy Ly). This dulls
colors that are out of gamut, giving a good impression of
how their CMYK equivalents will look. Again, try this with the
file RGB Gamut.jpg on the CD – you’ll be astonished by the
difference.
When working for CMYK, it’s common practice to switch
in and out of Proof Colors mode frequently, to check that the
colors will work: any that look significantly different when
proofed in this way will need to be changed.
Alternatively, you can turn on Gamut Warning mode using
CSy LSy. This turns all out-of-gamut colors
to a flat gray, as shown here. It can be shocking to see how
much of that bright color you’ll lose!
How to Cheat in Photoshop CC
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