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EspañolABSOLUTE COLOR SPACE
(Redirected from Absolute colour space)
In color science, there are two meanings of the term 'absolute color space':
★ A color space in which the perceptual difference between colors is directly related to distances between colors as represented by points in the color space.[1][2]
★ A color space in which colors are unambiguous, that is, where the interpretations of colors in the space are colorimetrically defined without reference to external factors.[3]
In this article, we concentrate on the second definition, which is the one more often encountered in current use.
CIEXYZ and sRGB are examples of absolute color spaces, as opposed to a generic RGB color space.
A non-absolute color space can be made absolute by defining its ingredients more precisely. For instance, if the red, green, and blue colors in a monitor are measured exactly, together with other properties of the monitor, then RGB values on that monitor can be considered as absolute.
A popular way to make a color space like RGB into an absolute color is to define an ICC profile, which contains the attributes of the RGB. This is not the only way to express an absolute color, but it is the standard in many industries. RGB colors defined by widely accepted profiles include sRGB and Adobe RGB. The process of adding an ICC profile to a graphic or document is sometimes called tagging; tagging therefore marks the absolute meaning of colors in that graphic or document.
One absolute color can be converted to another absolute color, and back again, in general; however, each color space has its own gamut, and converting colors that lie outside that gamut will not produce correct results. There are also likely to be rounding errors, especially if the popular range of only 256 distinct values per component (8 bits) is used.
Also note that one part of the definition of an absolute color is the viewing conditions. The same color, viewed under different natural or artificial lighting conditions, will look different. Those involved professionally with color matching may use viewing rooms, lit by standardized lighting.
Occasionally, there are precise rules for converting between non-absolute color spaces. For example HLS is defined as a mapping of RGB. Both are non-absolute, but the conversion between them should maintain the same color. However, in general, converting between two non-absolute color spaces (for example, RGB to CMYK) or between absolute and non-absolute color spaces (for example, RGB to L
★ a
★ b
★ ) is almost a meaningless concept, though there will be formulae that give roughly equivalent results.
A different method of defining absolute color spaces is familiar to many consumers as the swatch card, used to select paint, fabrics, and the like. This is a way of agreeing a color between two parties. A more standardized, but still proprietary, method of defining absolute colors is Pantone, which includes swatch cards and recipes that commercial printers can use to make inks that are a particular color.
1. Industrial Color Testing: Fundamentals and Techniques, Hans G. Völz, , , Wiley-VCH, 2001,
2. Industrial Inorganic Pigments, Gunter Buxbaum and Gerhard Pfaff, , , Wiley-VCH, 2005,
3. Java 2D Graphics, Jonathan B. Knudsen, , , O'Reilly, 1999,
★ Cambridge in Colour: Colour Space Conversion
In color science, there are two meanings of the term 'absolute color space':
★ A color space in which the perceptual difference between colors is directly related to distances between colors as represented by points in the color space.[1][2]
★ A color space in which colors are unambiguous, that is, where the interpretations of colors in the space are colorimetrically defined without reference to external factors.[3]
In this article, we concentrate on the second definition, which is the one more often encountered in current use.
CIEXYZ and sRGB are examples of absolute color spaces, as opposed to a generic RGB color space.
A non-absolute color space can be made absolute by defining its ingredients more precisely. For instance, if the red, green, and blue colors in a monitor are measured exactly, together with other properties of the monitor, then RGB values on that monitor can be considered as absolute.
A popular way to make a color space like RGB into an absolute color is to define an ICC profile, which contains the attributes of the RGB. This is not the only way to express an absolute color, but it is the standard in many industries. RGB colors defined by widely accepted profiles include sRGB and Adobe RGB. The process of adding an ICC profile to a graphic or document is sometimes called tagging; tagging therefore marks the absolute meaning of colors in that graphic or document.
| Contents |
| Conversion |
| Other absolute color spaces |
| References |
| External links |
Conversion
One absolute color can be converted to another absolute color, and back again, in general; however, each color space has its own gamut, and converting colors that lie outside that gamut will not produce correct results. There are also likely to be rounding errors, especially if the popular range of only 256 distinct values per component (8 bits) is used.
Also note that one part of the definition of an absolute color is the viewing conditions. The same color, viewed under different natural or artificial lighting conditions, will look different. Those involved professionally with color matching may use viewing rooms, lit by standardized lighting.
Occasionally, there are precise rules for converting between non-absolute color spaces. For example HLS is defined as a mapping of RGB. Both are non-absolute, but the conversion between them should maintain the same color. However, in general, converting between two non-absolute color spaces (for example, RGB to CMYK) or between absolute and non-absolute color spaces (for example, RGB to L
★ a
★ b
★ ) is almost a meaningless concept, though there will be formulae that give roughly equivalent results.
Other absolute color spaces
A different method of defining absolute color spaces is familiar to many consumers as the swatch card, used to select paint, fabrics, and the like. This is a way of agreeing a color between two parties. A more standardized, but still proprietary, method of defining absolute colors is Pantone, which includes swatch cards and recipes that commercial printers can use to make inks that are a particular color.
References
1. Industrial Color Testing: Fundamentals and Techniques, Hans G. Völz, , , Wiley-VCH, 2001,
2. Industrial Inorganic Pigments, Gunter Buxbaum and Gerhard Pfaff, , , Wiley-VCH, 2005,
3. Java 2D Graphics, Jonathan B. Knudsen, , , O'Reilly, 1999,
External links
★ Cambridge in Colour: Colour Space Conversion
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