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The Critically Important Color and Gamma Calibration Article


This article will explain how to understand and work with Photoshop's Color Management System (CMS), including how to create a custom profile, how to create an ICC profile for a monitor, how to set Photoshop's CMS defaults, how to use the Color Settings dialog box, and much more. It is excerpted from Inside Photoshop CS, by Gary D. Bouton. (Sams, 2004, ISBN: 0672326442).

Author Info:
By: Sams Publishing
Rating: 4 stars4 stars4 stars4 stars4 stars / 60
December 15, 2004
TABLE OF CONTENTS:
  1. · The Critically Important Color and Gamma Calibration Article
  2. · Understanding Photoshop's Color Management System (CMS)
  3. · International Color Consortium (ICC)
  4. · Translation, Please
  5. · Preparing to Create a Custom Profile
  6. · Install the Latest Drivers for Your Equipment
  7. · Setting Photoshop's Color Management Defaults
  8. · The Settings Drop-Down List
  9. · Choosing from the RGB Working Spaces Drop-Down List
  10. · Color Management Policies
  11. · Conversion Options: Which Engine to Use
  12. · Black Point Compensation
  13. · Assigned Profile
  14. · Color Management Policies in Action
  15. · Converting a Profile Means Changing the Data
  16. · Soft-Proofing, or Seeing Onscreen What an Image Will Look Like When It's Printed

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The Critically Important Color and Gamma Calibration Article - Understanding Photoshop's Color Management System (CMS)
(Page 2 of 16 )

Up 'til now, establishing a color-managed workflow was something attempted only by large organizations with big, fat budgets for equipment and dedicated color management technicians. And it didn't always work, even for them. Photoshop 5 introduced a color management process for the individual desktop, and Photoshop 5.5 improved upon that beginning. But those efforts fell short of being impressive; and most users, including us, continued to run, screaming, for the exits. Even talking about color management was too horrible to contemplate.

Well, times have changed. Adobe's new color management system (also referred to as CMS) is probably the single most important feature in Photoshop CS, in Illustrator 10, and in every other new Adobe product coming down the pipeline. Adobe deserves a lot of credit, but so do Apple and Microsoft and a whole bunch of other companies that make up the International Color Consortium (ICC). All these companies have made a serious commitment toward making color management work. It is now possible for mere mortals to understand and use color management. This is great news!

Having a usable system for managing color is a big deal. It is headline news. It is worth writing home about. Why? Because after you have set up your system to use color management and you've learned how to use these new color management tools, you'll never have to play the "What color is it, really?" game again. The colors you see on your monitor will be surprisingly close to what will come streaming out of a high-speed printing press or tumbling out of your desktop inkjet printer.

Adobe has made a splendid CMS that works the same in all of its products. Apple and Microsoft have done their part by providing operating system–level support for color management so that every program, even non-Adobe programs, can use color management. Equipment manufacturers have made descriptions of the color capabilities of their products available so that the information can be "plugged into" the CMS. Now you can master the concepts of color management and take up the new tools that have been placed at your disposal.

Coming to Terms with Color Management

To be frank, color management is still not an easy topic to understand, and you can't master it by reading a few paragraphs. But we promise you that it is possible to learn, that it is worth the effort, and that if you take your time going through this chapter, you will be able to use Adobe's CMS and still have enough brain cells left to do creative, artistic work.

In this section, we look at some of the key terms used in talking about color management. Along the way, you'll catch a little of the history of how this newest CMS evolved.

Color Spaces and Color Gamut

Throughout this chapter, you frequently are going to see the terms color spaces and color gamut, as coarsely described in Chapter 0, "Answers to the Most Important Imaging Questions." Color space is a model for representing color in terms of values that can be measured, such as the amount of red, green, and blue in an image. CMS works with standard color spaces, including RGB (Red, Green, Blue), LAB (L for relative lightness, A for relative redness-greenness, and B for related yellowness-blueness), and CMYK (Cyan, Magenta, Yellow, Black). Color gamut refers to a contiguous range of colors describing the limitations of a device or image. Color gamut might be called color capability when referring to a specific color space. "How many colors can this model represent?" is the question put forth by color gamut.

Life would be very boring and one-dimensional if the universe and every man-made device had only one color space. That's not the case, however, and so the issue of color gamut is a big concern for anyone involved in color-critical work. Here's a quick summary explaining why:

  • Every device—monitor, printer, printing press, camera, film, ink, and media combination—can produce only a limited number of colors.

  • No two devices or processes have the exact same color gamut.

  • Even two printers or monitors of the same make and model vary from each other, although new generations of desktop printers with built-in densitometer (color-measuring device) and automatic self-calibration tend to be reliable from printer to printer.

  • A device changes in its color-rendering capability because of age, lighting, or other operating conditions.

Ugh. These varying factors drive digital artists and production people up a virtual wall!

Color Calibration

Before you explore the Adobe CMS further, you need to calibrate your devices. What do we mean by the term calibrate? Calibration is the process of bringing a device, such as a printer or monitor, to an absolute standard to ensure consistency over time and across devices of the same make and model. That is, you are attempting to make the color gamut and characteristics of a physical device adhere to some empirical, mathematically perfect standard.

Calibration is critical when you want accurate color output on a monitor. A good place to start is to match the white point and gamma from monitor to monitor, using monitor calibration software such as Adobe Gamma, or third-party software and hardware when available.

Working Space

Time for a new term: working space, which includes RGB and CMYK color spaces. A working space is the pool of possible colors available when you edit a file. In the early days of color management, the monitor's color capability (color gamut) was the same as the space in which you worked with your image (the working space). If there were only one monitor in the world, and it never changed, you could consider the color gamut and the working space to be the same. But such is not the case, and a CMS shouldn't assume it is.

A much better idea is to assign actual numbers to specific color values (sometimes referred to as data) and then reference and manipulate the data within the context of an ideal, standard working color space, rather than use the settings of a fallible and limited physical device. How is such an ideal, a standard, established, when the world is full of so many different types of monitors, printers, scanners, and other devices? Read on!

Commission Internationale de l'Eclairage (CIE)

CMS creators needed a uniform way to describe the color space of devices and standard color spaces. They also needed to define a standard set of rules that govern the way information about color values is exchanged between color spaces that do not overlap.

In the 1930s, the Commission Internationale de l'Eclairage (CIE), based in France, began the task of establishing color standards by assigning numbers to every color visible to the human eye. The color spaces the CIE defined, such as CIELAB, form the foundation of device-independent color for color management. However, the group's work was only a beginning; it did not resolve the color management issues encountered in electronic publishing. Who had InDesign in 1930 :) ? 

This chapter is from Inside Photoshop CS,  by Gary D. Bouton. (Sams, 2004, ISBN:  0672326442). Check it out at your favorite bookstore today. Buy this book now.


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