Color Space

Color Space

In most cases, device-independent color definitions have three dimensions, and these dimensions make up what we call a color space. The dimensions are:

Hue: According to the American Heritage Dictionary, hue refers to a particular gradation of color such as a shade or tint, like “all the hues of the rainbow.” An individual frequency in the color spectrum. Humans are capable of discerning over 10 MILLION colors.

Saturation: This term refers to the vividness of hue or purity of a color. Intensity can be increased or decreased to suit.

Brightness or Luminance: (also called Value) The terms refer to the dimension of a color that can range from very dim (dark) to very bright (dazzling). A grayscale image is an example of an image represented with only the Luminance value.

Conventional four-color offset printing and most color digital printers use four colors – Cyan, Magenta, Yellow and Black – as subtractive primary colors to create a wide range of additional colors in what is known as four-color process. These four colors, referred to as CMYK, with “K” representing black, have long been the primary color space utilized in the world of printing. As mentioned earlier, CMY are the three primary subtractive colors, and when mixed in equal parts, in theory result in black. In reality, a dark color that is not a true black may result from less than ideal colorants, or impurities in the toner or ink components.

To economize on ink consumption and to produce deeper black tones, unsaturated and dark colors are produced by substituting black ink for the combination of cyan, magenta and yellow.

When an image is captured or created digitally — that is, scanned and captured with a digital camera, or created using desktop publishing software — it is commonly represented using red, green and blue (RGB) as this is the color language that your computer monitor requires. These colors are the additive primary colors that are mixed with light and used in displaying images on a screen. Here is a great video that shows you how to use this info to ensure your color palette will always harmonize when designing.

CMYK and RGB represent two very different color spaces. With the world’s increasing volume of digitally captured files, most of which are in RGB format, printers preparing a file for print must consider the color space in which various elements are created. Having the processes in place to convert these files as appropriate for the intended output device is equally important. To convert values obtained from an input device, such as RGB from a scanner or digital camera, into the device code values needed by an output (rendering) device, such as a CMYK printer, a transformation is needed to modify the data.

This role belongs to the ICC profile, which directs the actual color conversion produced by a color management module (CMM). The CMM uses the profiles to convert and match colors on one device’s color space to or from another device’s color space. When colors on one device’s gamut are displayed on a device with a different color gamut, the CMM attempts to minimize the perceived differences in the displayed colors between the two devices.

In general, you want to use color spaces that are as large as is practical. For example, if your printer is capable of producing output in a color space larger than sRGB, there is no reason to hobble your work by limiting output to the small sRGB gamut. If you do, you'll lose the saturated cyans and greens that can make your prints stand out.

Your applications and devices need to know what color space they are working with.

This most definitely includes your monitor. Without knowing what color space your monitor displays images in, it is impossible to accurately gauge how your images will appear in print. Calibration and profiling of your monitor is the first step towards a color managed workflow.

Most printers and all but a very few scanners or cameras either print or capture images in well-defined color spaces.

Larger color spaces contain both more colors and brighter, more saturated colors.

If your camera or scanner supports it, use a larger color space such as Adobe RGB.

Use sRGB for web graphics. This is at least in the same ballpark as most monitors. Using Adobe RGB for web images leads to washed-out looking colors in applications that are not color aware (i.e. most web browsers).

Your computer handles color differently than your monitor does, and differently than your print output requires. Your computer understands color in LAB colorspace, which we will discuss in detail later. The CMM translates from RGB to LAB and then from LAB to CMYK based upon ICC profiles. This interim colorspace is called Profile Connections Space (PCS) is either CIELAB (L*a*b*) or CIEXYZ.

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Email me at reilley4color@gmail.com