Digital Prints

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Mastering Digital Printing
RGB is device-dependent, which means that the color you end up with depends on the
device you send it to or the RGB space you define it in. This is what I call “The Circuit
City Phenomenon.” Go into any appliance store like Sears or Circuit City, and pay a visit
to the television department. Stand there in front of the wall of TVs for a moment, and
you will instantly understand the problems of working with color. Even though every TV
may be set to the same channel, all the screens look different! The same with digital devices.
Some have large color gamuts, some don’t. Some clip colors, some don’t. Fortunately,
advanced image-editors like Photoshop help you control some of these uncertainties.
Color Space Gamuts
One of the important, distinguishing characteristics
of each color space is its color gamut, which
defines the entire range of possible colors in that
system (it can also apply to material and devices
like monitors and printers). The larger or “wider”
the gamut, the more colors available. Although
most people believe that the gamut of RGB is
larger than that of CMYK, color expert Steve
Upton of CHROMiX explains that that’s a myth.
“I usually describe them as different and use ’a
circle drawn over a triangle so they both have
portions outside the other’ as a description.”
Figure 4.7 shows how some CMYK colors fall
outside the RGB gamut, making them unviewable
or clipped. This is also called being out-ofgamut,
or in color tent terms, outside the tent.
Also realize that these 2D diagram plots don’t tell
the whole story since they represent only one view
of a 3D color space.
RGB comes in several sub-varieties called RGB working spaces in Photoshop, which currently
only recommends four of them (see Figure 4.8). While all RGB files are generically
called “RGB,” when you’re actually working on images in Photoshop, you have the option
of picking different working spaces for them (starting with Photoshop 6, you no longer
have to choose only one). Leaving out the more obscure, from largest gamut to smallest,
the default RGB working spaces in Photoshop are: Adobe RGB (1998), ColorMatch RGB,
AppleRGB, and sRGB.
Adobe RGB (1998)
The is the largest of the default RGB color working spaces and a good choice for digital
artists. It pretty much covers the gamut range of the common CMYK devices including
inkjets plus digital photo printers. You’ll rarely be out of gamut with Adobe RGB, yet it’s
not as unwieldy as the larger LAB space.
Figure 4.7 The different gamuts of two
sample RGB and CMYK color spaces.
Graphing by CHROMiX ColorThink