In previous articles on color management, we’ve explored factors that affect color output, and presented concepts and tools to better manage these factors in developing a proper color management process. In this, the sixth in a series on color management, we’ll look at standards in the industry and how they are used.
There are many different devices used in digital printing that represent color in a manner meaningful to that device. The range of colors that a device can represent varies as the underlying technology varies. To better understand the need for standards in communicating color, we’ll first look at differences in devices.
Monitor
A monitor presents color by emitting light. The color space used by monitors is referred to as “RGB”, which represents the primary colors Red, Green and Blue. This color model is additive, which starts with no light (black), then primary colors are added together in varying intensities to present an array or colors.
A monitor can be thought of as a grid of thousands of tiny red, green and blue lights, each with its own dimmer to control intensity. The set of all possible resulting colors is the “gamut” defined by those particular lights.
Printer
Printers use a subtractive color model referred to as CMYK, for the primary ink colors used: Cyan, Magenta, Yellow and Key (or black). The CMYK model assumes white as a start point – this is your paper or print media. Cyan is the complement of Red, meaning Cyan acts as a filter that absorbs red. In printing to white media, the amount of Cyan ink applied will control how much red will show. Magenta is the complement of green and yellow is the complement of blue. Combinations of different amounts of these 3 inks can produce a wide range of colors. Black ink is included in this model to save money on ink and to produce richer blacks – an alternative to using all 3 base colors to produce black.
Since RGB and CMYK color spaces are device dependent, there is no simple conversion formula that converts between them when moving a digital color representation between devices. Movement between devices is a natural part of the production process, from a design station to a printer for example. This conversion between devices and corresponding color spaces is typically handled by color management systems using profiles that describe the spaces being converted.
ICC
The International Color Consortium was formed by industry vendors to create a universal color management system. Their stated purpose is to promote the use of color management systems that are vendor and platform independent.
The ICC has defined a format for profiles which describes the color attributes of a particular device by mapping between the source device’s color space and a profile connection space (PCS) to which other devices can be mapped. The PCS can be thought of as a theoretical and device independent color space capable of defining any and all colors. Each device’s color gamut is a subset of PCS, so the PCS serves as a device independent common ground to facilitate device dependent color mapping – a translator of sorts.
Pantone Matching System
PMS, or Pantone Matching System is a de-facto standard for color reproduction. Pantone produces color fan decks to be used as reference colors in design and production. As a common reference, these guides can be used by manufacturers in different locations to communicate color without direct contact with one another.
RGB Color Spaces
A color space is a definition, range or “gamut” of possible colors that can be represented. An RGB color space is an additive color space, meaning that starting with black, some combination of the primary colors Red, Green and Blue are added in varying intensities to produce a wide array of colors. The most commonly used RGB color spaces are sRGB and Adobe RGB.
sRGB was proposed by Microsoft and HP as it approximates the color gamut of most common computer display devices. Adobe RGB has a significantly broader gamut, and was designed by Adobe to encompass most of the colors on a CMYK printer, but by using only RGB primary colors on RGB display devices.
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