ChromaticSoul :: The Blog

Color Management Part I

Posted on: 4 May 2007

Do these words bother anyone other than me? Color Management. This term can be so nebulous as to be confused with color calibration, color profiling or perhaps include both and all of the above. So for the next couple of days I’d like to devote some time to a discussion of color management. My first visit is to wikipedia–the www encyclopedia of the world. I went to first find out what a working definition of color management is.

In digital imaging systems, color management is the controlled conversion between the colors of various color devices, such as scanners, digital cameras, monitors, TV screens, film printers, printers, offset presses, and corresponding media. The primary goal of color management is to obtain a good match across color devices; for example, a video which should appear the same color on a computer LCD monitor, a plasma TV screen, and on a printed frame of video. Color management helps to achieve the same appearance on all of these devices, provided the devices are capable of delivering the needed color intensities (via wikipedia).

What is a Color Management System (CMS)? and
Why Do We Need a CMS?

I think it is fair to say that as photographers we can all agree with the goal of a Color Management System (CMS) is to provide color consistency and predictability between devices. According to Digital Outback Photo, color management systems take various forms, but at their most basic,

…they consist of three core elements: an engine that transforms color contained in images and documents, device profiles that represent the color capabilities of a printer, monitor, scanner, or camera, and an interface that allows users or applications to utilize and manage the capabilities of the system (via Digital Outback Photo).

Consider the following analogy:

In many ways, communication in color has problems similar to those with communication in languages. Each device is like a person, speaking his or her own language. When one person that speaks French attempts to communicate with another person that speaks Japanese, there is a breakdown, and the message is not communicated accurately, if at all. What’s needed is an interpreter that is capable of interpreting the language as well as the dialect, to ensure that the message is properly communicated. The same holds true for color reproduction (via Digital Outback Photo).

Now as far as “languages” go, most monitors and cameras “speak” in red, green, and blue (RGB), while printers and scanners are bilingual and can “speak” RGB and cyan, magenta, yellow, and black (CMYK). Add to this the human eye which can see (“speak”) far more colors (millions) than any device on today’s market.

So we begin to notice problems when the colors seen on our display are much brighter and more saturated than the color that comes out on the printer. The reason for this is likely that the the color on the display is in gamut for the display, but is not in gamut for the printer. Let’s say for instance you want to represent the purest red you can possibly get. In that case you’re probably thinking about red that in Photoshop RGB is notated as R-255, G=0, B=0. This purest red will visually look different depending on whether you are viewing it via a scanner, a CRT-monitor, a LCD-monitor, a digital camera, or a printer. In this case, the color is said to be device dependent–the desired appearance of color depends on its being reproduced on a particular device. Several different factors determine which color is substituted for the original color, better known as gamut mapping.

Another challenge exists in the method that desktop devices communicate with each other. It’s typical to have a camera, display and printer from three different manufacturers, as well as image manipulation and page layout software from different software vendors. But none of these devices communicate in the same language of color, and many handle color differently–much like the example of human speech.

Color management systems link these disparate pieces together, and attempt to provide a consistent way for devices and applications to interpret color data. The characterization of a device is also called ‘profiling.’ Modern operating systems and imaging editing applications use the International Color Consortium’s (ICC) color management model that has ICC colour profiles at its core. Profiles that are custom-created for the device at hand tell applications how to compensate for the specific interpretation of each color by the device. Most manufacturers of monitors, scanners and printers deliver standard profiles with their devices.  We’ll discuss color profiles in Part II.

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