The CMYK Color Model

The CMYK color model uses four primary colors to define a color: cyan (C), magenta (M), yellow (Y), and black (K). CMYK was designed for printing, where incoming light is reflected by the print.

CMYK is a subtractive color model, as each of the colored inks absorbs (subtracts) a certain component of the incident light. Figure 3-3 shows that mixing cyan and magenta gives you blue, and when you add magenta to yellow you get red. In theory, the combination of the colors C, M, and Y alone should be sufficient to produce black, but due to certain impurities in inks, they produce a dark muddy brown instead. To solve this problem, a fourth (black) color is added, and is called the key color (K for short).

Although CMYK is an important color model for industrial printing processes, it is not used much in digital photography. Though inkjet printers are technically CMYK printers (most are even CcMmYK with additional light cyan and light magenta inks), they provide the user with an RGB interface. Transformation from RGB to CMYK is performed by the printer driver as a background process.

We rarely use the CMYK color model in our workflow. Even when preparing images that requires CMYK for printing, you should stick to using RGB mode whenever possible and resort to an RGB-to-CMYK conversion at the very last step. After conversion, some additional sharpening and some slight increase in saturation may be required. Working on photos in CMYK mode has the following distinct disadvantages:

► CMYK image files are larger than RGB files because they have four color values per pixel instead of three.

► Some photo filters do not work in CMYK mode.

Magenta

Blue

Figure 3-1: The RGB color model

Magenta

Blue

Figure 3-1: The RGB color model

Figure 3-2: The L*a*b* color model

Figure 3-2: The L*a*b* color model

Blue

Cyan

Blue

Cyan

Magenta

Green

Yellow

Figure 3-3: The CMYK color model

Magenta

Green

Yellow

Figure 3-3: The CMYK color model b a

> A color space consists of all the colors ► The CMYK color space usually contains fewer colors than most RGB that a specific device (or device class) can color spaces. This means that when you convert an image from RGB to

"see" or reproduce. CMYK, you probably lose some colors. There is no way to retrieve lost colors if you want to use your image later for Lightjet direct printing on photographic paper or for a digital presentation on an RGB monitor.

> If you have to convert a photo from RGB to CMYK, make a copy of your image file and convert that.

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

Get My Free Ebook


Post a comment