List of color spaces
This is a list of the color spaces with notes on how to use them. A color space is based on a color model and is at the same time a specific mapping of this color model in a general color space. A large number of color spaces are used around the world today.
Models
There are six main models that can be divided into subordinate models: CIE, LAB, RGB, YUV, HSL / HSV and CMYK.
Tristimulus
CIE 1931 XYZ
This is the first attempt to create a sound color space. It was based on the measurement of human color perception and is the basis of all other color spaces.
CIELUV
CIELUV is a modification of CIE 1931 XYZ to show the color differences a little better and more precisely. Because of its linear properties, the CIELUV room is particularly suitable for additive color mixing of light colors.
CIELAB
The aim of CIELAB (L * a * b *, Lab) is to make the color space more linear in terms of perception. This means that a numerically identical change in a color value also means an identical change in the visual evaluation. CIELAB is mostly understood as an alternative to the related Lab color space "Hunter Lab". This color space is generally used for surface colors, but not for blending them with translucent lights.
CIEUVW
CIEUVW (also called UCS) applies to measurements over a larger field of view than CIE 1931 XYZ and its values differ slightly. A transformation of X 10 , Y 10 , Z 10 is also included.
Red-Green-Blue
RGB (on red, green, blue) describes which “type of light” has to be emitted in order to achieve a given color. Light is put together from the "darkness". RGB has separate values for red, green and blue. RGB itself is actually not a color space, but rather the color model. There are many different RGB color spaces for this color model, some of which are listed.
RGBA is an RGB with an additional alpha channel that notes the transparency of the RGB point or the R, G and B values.
sRGB
The sRGB color space , or standard RGB (Red-Green-Blue), is an RGB color space that was jointly developed by Hewlett-Packard and Microsoft for use on the Internet . It has been endorsed and adopted by W3C , Exif , Intel , Pantone , Corel, and other industrial companies, and is used for open source software such as GIMP . sRGB is used for both company-specific and open graphic formats such as SVG .
sRGB is seen as the common color space used to generate images for viewing on the World Wide Web . The resulting color space corresponds to a gamma of 2.2 , the average voltage level of CRT displays at that time.
Adobe RGB
The Adobe RGB was 1998 Adobe Inc. developed. The aim was to reproduce a maximum number of colors from a CMYK printer on an RGB color source such as a computer display. The Adobe RGB can represent about half of the visible colors from the Lab color space. The gamut of sRGB has been significantly improved in the cyan and green .
Adobe Wide Gamut RGB
The Adobe Wide Gamut RGB was developed as an RGB color space by Adobe as a direct alternative to standard RGB. It can store a larger area than sRGB. The wide gamut color space is an extended version of Adobe 1988 RGB. For comparison: With Wide Gamut, 77.6% of the visible colors of the Lab room can be determined, with standard Adobe RGB it is only 50.6%.
One disadvantage is that around 8% of this color space is imaginary colors . These are not visible colors and cannot be represented by any medium. This means that these "unnecessary colors" ultimately waste color space, ie reduce the accuracy of the color space to be displayed.
More RGB spaces
The result is a long list of other RGB color spaces. With new red, green and blue selections and different gamma values, everyone can create a new color space, as seemed useful for the ProPhoto RGB color space , for example .
Luminance plus color
YIQ, YUV, YDbDr
YIQ was used in the NTSC television standard (North America and Japan) for historical reasons. This color system stores a brightness value and two chrominance values, which roughly correspond to the blue and the red of the color. Its structure corresponds to the YUV scheme of the PAL television standard (Australia and Europe, with the exception of France with its SECAM ), only that it is rotated by 33 ° against YIQ. The YDbDr scheme is used in SECAM color television and has a different twist in color.
YPbPr, YCbCr
YPbPr is a differently scaled version of YUV, which is mostly used in the digital form as YCbCr . It is widely used in video and image compression , such as MPEG and JPEG .
xvYCC
xvYCC is a new international standard color space for digital videos and is based on the ITU BT.601 and the BT.709 , although the color gamut is stipulated by extended R / G / B specifications ( primaries ) of this standard.
Hue and saturation
HSV
The coordinates of the HSV or HSB color space are described with H = Hue (hue), S = Saturation (saturation) and V = Value (light value) or B = Brightness (brightness). It is more popular with artists because it does more justice to the natural “thinking in terms of colors”, since the change in color value or saturation fits better with the idea of colors than additive or subtractive color components. HSV is ultimately a transformation of an RGB color space and the color measurement is derived from this.
HSL
HSL and HSI are also structured, with the hue (H) and saturation (S) either L = luminance or lightness, i.e. luminosity, or I = intensity (of light) being added to three-dimensionality. Brightness as clarity stands for a pure color with the brightness of white, lightness as brightness refers to a medium, neutral gray.
CMYK
CMYK comes from four-color printing with process colors and describes the nature and structure of the printing inks. The light reflected from the substrate (often paper) is influenced by the printing inks in such a way that the desired color is created in the impression. Starting with the (mostly) white substrate, the printing inks subtract so much from the “white” through their layer structure that the desired image is created. The (print) color values for cyan, magenta, yellow and black are stored in the CMYK space. Virtually every set of printing inks, every substrate and every printing task has its own CMYK color space. The printing task here is to be understood as the formation of dots, the color transition of each printing color (with all its production differences) and the respective technological requirements.
"Material" color spaces
Material color space means that the colors are reproduced with patterns in different forms and on different materials. Color collections, color catalogs and, in the simplest case, color fans present a color space of the selected colorants on a defined substrate. Due to the mixture, they still have a three-dimensional structure. In the case of the aforementioned (mathematical-abstract) spaces, color coordinates can be specified and recorded using measurement technology. However, these material samples are immediately perceptible.
Special color spaces
The RG color space of the color types is developed for machine vision . Only the color of the light is evaluated (red, yellow, green), but not its relative brightness as dark or light. For orientation in artificial vision, for example by robots, only the chromatic type is used here as a fixed variable, not that of the viewing angle dependent brightness selected.
The LMS color space is the perception color space based on the feedback from the cones in the retina of the eye. It is commonly used in psychometric research.
Outdated color spaces
The early technical color spaces only had two components. With them the blue part of the light was ignored. In the (historical) transition from a black and white image or a monochromatic image to a color image, a technically much more complex three-component process only produced a slightly better color fidelity than the technically simpler two-color image. This subheading includes the RG color space of the early Technicolor films and the RGK color space of red, green and black in early color printing.
Individual evidence
- ↑ a b Keith McLaren: Dyes, General Survey . In: Ullmann's Encyclopedia of Industrial Chemistry . Wiley-VCH. June 15, 2000
- ↑ Bruce Lindbloom
