Quality Control for Color

When I use the term color management, I'm talking about predicting color from a variety of sources. Color management is most effective and most achievable when you, the creative, control the majority of the process or when your production partner is creating both your scans as well as your output.

Color management involves the proper calibration of devices. To calibrate means to ensure that your devices are functioning according to manufacturers' specifications. Often manufacturers provide methods for achieving calibration.

Next, color management involves the characterization of each device. To characterize a device means to describe the device in terms of the number of colors it is capable of capturing, displaying, or producing. This characterization is stored in the form of a profile, which is a digital color story attached to an image file.

Finally, color management often involves conversion from one color mode to another. For print, that might be converting from RGB to CMYK. For web, it might be the opposite. As you repurpose content for alternative distribution methods, converting from one color model to another becomes commonplace and you must understand what is happening when you convert.

The l*a*b color space is an internationally accepted color model that many conversion utilities use to translate color from one color mode to another. The l*a*b space is device independent and is an ideal communicator between other color models. So, when you take an RGB color and convert it to CMYK, it passes through the l*a*b color space and the equivalent is found, defined, and then mapped to the closest corresponding color on the other side.

Approximately 16 million colors make up the RGB color gamut. You can create approximately 5,000 colors with CMYK, but the indexed color models associated with web graphic file formats limit your color palette to 256 colors. Going from 16 million to 256 is a big difference. There can be no doubt that colors will change throughout these transitions.

Add to that differences in manufactured monitors and monitor technologies, lighting, and computer platform specifications, and you can see how difficult color management can be to achieve.

Then there's the human factor. How we each interpret those light waves is another matter. I might see mauve and someone else might see purple. Many people have deficiencies that affect the way they see color. Color tests can ferret out those deficiencies, and anyone working in color should be color tested.

Having said this, if you want to evolve into a color-managed workflow, your Adobe productsincluding InDesign CS2allow for color management by using color descriptions that are called International Color Consortium (ICC) color profiles. ICC profiles are descriptions of color within the file based on specific devices, such as scanners, monitors, proofers, and presses. These profiles quantify the behavior of these devices so that printed outcomes can be predictable with proper quality control and calibration practices.

For example, say your print service provider is producing your image scans as well as creating final output from their printing presses. This vendor has taken great care and time to make sure these images will print consistently and predictably on their press. When you receive their scans to further work with them in Photoshop or place them in InDesign, you will likely get a message that the image has an embedded profile. You will need to keep and not discard the profile because this profile has compensated for the differences between the color the scanner has captured versus the color the press can print.

Note

Although the topic of color management is outside the scope of this book, features and commands are available in InDesign: Go to the Edit pull-down menu and select Color Settings. Read about color management in your Adobe user guides. You will also find good publications on the subject from Graphic Arts Technical Foundation (GATF) at www.gain.net.