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- Adobe RGB has a wider gamut than sRGB and is often used when the goal
is making high-quality prints. One drawback is that images using this color
have subdued colors when displayed on a display because almost all displays
are based on the sRGB color space. However, if you use this space, Photo-
shop, Lightroom and other products can convert it to sRGB without any loss
in quality.
- ProPhoto is the largest color space currently used in digital photography
and the only one that has a gamut that includes all of the colors a camera
can capture. This color space can cause problems when used with 8 bit JPEG
images. There are so many fewer levels of tones (256 versus a RAW image’s
65,536) that if you make any large adjustments to the image you may get
banding, noticeable transitions in what should be smooth gradations.
- CIE LAB (pronounced “see-lab”), and its very closely related CIE XYZ,
are different but important kinds of color spaces although you don’t interact
with them directly. Unlike the other color spaces CIE LAB arranges colors
based on how we perceive them rather than on any particular device. For
this reason this color space is called “device-independent” (although if there
were a device, it would be the human eye). The space contains almost all of
the colors a human can perceive. (Interestingly, the actual CIE LAB color
model can’t be accurately printed or displayed because no device has all of
the required colors.) In the section that follows on color management you’ll
see how this color space plays an important role in moving images from the
camera to the screen and then to the printer while keeping colors constant on
all of these different devices.
- Working space. When editing an image, the editing application lets you
select a working space so the colors are what you expect to see when you
display or print the image. The working space can be sRGB, Adobe RGB, Pro-
Photo RGB or any other space supported by the application.
Although a color space is initially embedded in a JPEG image by the camera
that captured it there are two ways to change the color space.
- Attaching a new color space changes the look and colors of the image
without changing the color values of each pixel.
- Converting to another color space keeps the image looking the same,
but converts the color values of each pixel to fit into the new color space.
When using Photoshop you can assign different profiles and watch the image
change appearance as you do so. This is a good way to find the space that
works best for a particular image. The widest possible gamut isn’t always the
best choice. A smaller gamut such as sRGB has smaller spaces between the
colors so smooth gradations, such as those found in skin tones, are repro-
duced more faithfully. However, if the center of interest in the image is a fluo-
rescent orange traffic cone, most of its colors might be outside of the sRGB’s
gamut so ProPhoto would be a better choice.
CMYK uses cyan,
magenta, yellow (and
black) to form all other
colors.
TiPs
- In color manage-
ment, the term
“space” is so widely
used that it’s lost
any specific mean-
ing other than the
distribution of rGB
CmyK Colors
a three dimensional
chart that shows
their relationships.
- the CmY color
model is more often
called CmYK with
the “K” standing for
black. Black is need-
ed because although
mixing CmY at 100%
should create black,
it’s a muddy black.
sRGB’s gamut plotted
against the larger CIE
LAB.
Color mAnAgement—Color models And Color spACes
