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Color Space

Explanations > Perception > Visual Perception > Color Space

Description | Example | Discussion | So what?

Description

A 'color space' describes two things:

• The range of colors that are available within any system, such as a computer, an image file and a printed photograph.
• A standard way of holding these colors, so that when this color standard is known, other systems can reproduce the correct colors.

There are a number of common color spaces used, including:

• CIE 1931: An international standard to describe all visible colors.
• sRGB: A common standard used by computers and digital cameras.
• Adobe RGB 1998: A standard defined by Adobe, which allows for more colors to be represented than by sRGB.
• Prophoto: A standard that allows for even more colors to be represented than Adobe RGB 1998, and approaching full coverage of the CIE color space.
• Pantone: A standard set used by printers for many years.
• LAB: Based on the opponent process model.

Color spaces are often shown on a two-dimensional graph, where the x and y axes are calculated from the colors used. As the CIE space represents all visible colors, more limited color spaces are often shown superimposed on these. For example:

Example

A digital camera has the option of using either sRGB or Adobe RGB color spaces. A professional user chooses Adobe as it registers more colors.

A printing professional uses Pantone, which is the standard for the industry.

Discussion

It can be important to note that many devices do not show all available colors. This is typically due to the digital limitations, such as only using 8 bits for each of Red, Green and Blue. Indeed, while the eye is analog and can hence detect an infinite number of colors, any digital system is limited by the number of bits used. Having said this, while the eye can detect many colors, there comes a point where we are unable to consciously differentiate between two very similar colors.

The choice of color space will depend on a number of factors, including:

• The extent of colors that are required to be displayed.
• The file size for images that will be required (more colors means bigger file).
• The capability of instruments and systems used to display colours (including camera, printer and editing software).
• The compatibility of the color space with instruments and systems used.
• The requirements of other people to whom an image file may be given.

So what?

When doing color work, decide on the color space you need depending on the above factors. The two most important ones of these are typically 'numbers of colors' and 'compatibility'. While the former is desirable, the latter tends to be a practical constraint. A typical approach photographers use is to start by taking as many colors as possible (eg. by selecting 'Adobe' in the camera menus) and then converting down to the format that customers and collaborators can handle (such as sRGB). It is particularly worth remembering that computer displays usually only display 8-bit sRGB, even though editing software and printers can handle far more colours.

See also

Twelve Color Wheel