AdobeRGB is a color space introduced in 1998 by Adobe Systems Inc. AdobeRGB has a wider range of color reproduction areas such as green and blue. Adobe RGB provides 35% bigger in space than sRGB but both can display 16.7 million colors. Adobe Ps can now able to store image data, according to the AdobeRGB color space.
The CIE 1931 xy chromaticity diagram showing the primaries of the Adobe RGB (1998) color space. The CIE Standard Illuminant D65 white point is shown in the center.
For print workflows, Adobe RGB is generally more aligned with prepress color spaces. This isnât surprising; Adobe RGB exists in part because Adobe wanted to have an RGB color space that included CMYK colors that fall outside of sRGB. Whether the difference matters to you depends on the CMYK standard you use. On a DCI-P3 monitor, will I be missing color if I use an Adobe RGB working color space? If so, which space is the one to use? The differences in the two are rather tiny. Adobe RGB (1998) is red plot, DCI-P3 is Green. There are some areas of color space one is larger than the other, and vise versa. Using Adobe RGB is one of the leading causes of colors not matching between monitor and print. SRGB is the world's default color space. Use it and everything looks great everywhere, all the time. Adobe RGB should never be used unless you really know what you're doing and do all your printing yourself. If you really know what you're doing and working in publishing, go right ahead and use it. Adobe RGB is introduced by Adobe to cover up the lack of color space in sRGB, which technically is better when converted to a CMYK color spacet. It covers 52.1% of CIE 1931 color space. Many professionals process their works with Adobe RGB due to its wider color space.
The Adobe RGB (1998) color space is an RGB color space developed by Adobe Systems, Inc. in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, but by using RGBprimary colors on a device such as a computer display. The Adobe RGB (1998) color space encompasses roughly 50% of the visible colors specified by the CIELAB color space â improving upon the gamut of the sRGB color space, primarily in cyan-green hues.
Historical background[edit]
Beginning in 1997, Adobe Systems was looking into creating ICC profiles that its consumers could use in conjunction with Photoshop's new color management features. Since not many applications at the time had any ICC color management, most operating systems did not ship with useful profiles.
Lead developer of Photoshop, Thomas Knoll decided to build an ICC profile around specifications he found in the documentation for the SMPTE 240M standard, the precursor to Rec. 709. SMPTE 240M's gamut was wider than that of the sRGB color space, but not by much. However, with the release of Photoshop 5.0 nearing, Adobe made the decision to include the profile within the software.
Although users loved the wider range of reproducible colors, those familiar with the SMPTE 240M specifications contacted Adobe, informing the company that it had copied the values that described idealized primaries, not actual standard ones. The real values were much closer to sRGB's, which avid Photoshop consumers did not enjoy as a working environment. To make matters worse, an engineer had made an error when copying the red primary chromaticity coordinates, resulting in an even more inaccurate representation of the SMPTE standard.
Adobe tried numerous tactics to correct the profile, such as correcting the red primary and changing the white point to match that of the CIE Standard Illuminant D50, yet all of the adjustments made CMYK conversion worse than before. In the end, Adobe decided to keep the 'incorrect' profile, but changed the name to Adobe RGB (1998) in order to avoid a trademark search or infringement.[1]
Specifications[edit]Reference viewing conditions[edit]
In Adobe RGB (1998), colors are specified as [R,G,B] triplets, where each of the R, G, and B components have values ranging between 0 and 1. When displayed on a monitor, the exact chromaticities of the reference white point [1,1,1], the reference black point [0,0,0], and the primaries ([1,0,0], [0,1,0], and [0,0,1]) are specified. To meet the color appearance requirements of the color space, the luminance of the monitor must be 160.00 cd/m2 at the white point, and 0.5557 cd/m2 at the black point, which implies a contrast ratio of 287.9. Moreover, the black point shall have the same chromaticity as the white point, yet with a luminance equal to 0.34731% of the white point luminance.[2] The ambient illumination level at the monitor faceplate when the monitor is turned off must be 32 lx.
As with sRGB, the RGB component values in Adobe RGB (1998) are not proportional to the luminances. Rather, a gamma of 2.2 is assumed, without the linear segment near zero that is present in sRGB. The precise gamma value is 563/256, or 2.19921875. In coverage of the CIE 1931 color space the Adobe RGB (1998) color space covers 52.1%.[3]
The chromaticities of the primary colors and the white point, both of which correspond to the CIE Standard Illuminant D65, are as follows:[2]
The corresponding absolute XYZtristimulus values for the reference display white and black points are as follows:[2]Laser physics complete pdf.
Normalized XYZ tristimulus values can be obtained from absolute luminance XaYaZa tristimulus values as follows:[2]
where XKYKZK and XWYWZW are reference display black and white points in the table above.
The conversion between normalized XYZ to and from Adobe RGB tristimulus values can be done as follows:[2]
ICC PCS color image encoding[edit]
An image in the ICC Profile Connection Space (PCS) is encoded in 24-bit Adobe RGB (1998) color image encoding. Through the application of the 3x3 matrix below (derived from the inversion of the color space chromaticity coordinates and a chromatic adaptation to CIE Standard Illuminant D50 using the Bradford transformation matrix), the input image's normalized XYZ tristimulus values are transformed into RGB tristimulus values. The component values would be clipped to the range [0, 1].[2]
The RGB tristimulus values are then converted to Adobe RGB R'G'B' component values through the use of the following component transfer functions:
The resulting component values would be then represented in floating point or integer encodings. If it is necessary to encode values from the PCS back to the input device space, the following matrix can be implemented:
Comparison to sRGB[edit]Gamut[edit]
A comparison of the Adobe RGB (1998) color space and sRGB color gamuts space within the CIE 1931 xy chromaticity diagram. The sRGB gamut is lacking in cyan-green hues.
sRGB is an RGB color space proposed by HP and Microsoft in 1996 to approximate the color gamut of the most common computer display devices. Software for nutritionists. Since sRGB serves as a 'best guess' metric for how another person's monitor produces color, it has become the standard color space for displaying images on the Internet. sRGB's color gamut encompasses just 35% of the visible colors specified by CIE, whereas Adobe RGB (1998) encompasses slightly more than 50% of all visible colors. Adobe RGB (1998) extends into richer cyans and greens than does sRGB â for all levels of luminance. The two gamuts are often compared in mid-tone values (~50% luminance), but clear differences are evident in shadows (~25% luminance) and highlights (~75% luminance) as well. In fact, Adobe RGB (1998) expands its advantages to areas of intense orange, yellow, and magenta regions.[4]
Although there is a significant difference between gamut ranges in the CIE xy chromaticity diagram, if the coordinates were to be transformed to fit on the CIE uâ²vâ² chromaticity diagram, which illustrates the eye's perceived variance in hue more closely, the difference in the green region is far less exaggerated. Also, although Adobe RGB (1998) can theoretically represent a wider gamut of colors, the color space requires special software and a complex workflow in order to utilize its full range. Otherwise, the produced colors would be squeezed into a smaller range (making them appear duller) in order to match sRGB's more widely used gamut.
Bit depth distribution[edit]
Although the Adobe RGB (1998) working space clearly provides more colors to utilize, another factor to consider when choosing between color spaces is how each space influences the distribution of the image's bit depth. Color spaces with larger gamuts 'stretch' the bits over a broader region of colors, whereas smaller gamuts concentrate these bits within a narrow region.
A similar, yet not as dramatic concentration of bit depth occurs with Adobe RGB (1998) versus sRGB, except in three dimensions rather than one. The Adobe RGB (1998) color space occupies roughly 40% more volume than the sRGB color space, which concludes that one would only be exploiting 70% of the available bit depth if the colors in Adobe RGB (1998) are unnecessary.[4] On the contrary, one may have plenty of 'spare' bits if using a 16-bit image, thus negating any reduction due to the choice of working space.
See also[edit]References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Adobe_RGB_color_space&oldid=914080686'
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RGB-Cube
An RGB color space is any additivecolor space based on the RGB color model.[1] A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors.[2] The complete specification of an RGB color space also requires a white point chromaticity and a gamma correction curve. As of 2007, sRGB is by far the most commonly used RGB color space.
RGB is an abbreviation for redâgreenâblue.
Intuition[edit]
Comparison of some RGB and CMYK colour gamuts on a CIE 1931 xy chromaticity diagram
An RGB color can be understood by thinking of it as all possible colors that can be made from three colored lights for red, green, and blue. Imagine, for example, shining three lights together onto a white wall in a dark room: one red light, one green light, and one blue light, each with dimmers. If only the red light is on, the wall will be red. If only the green light is on, the wall will look green. If the red and green lights are on together, the wall will look yellow. Dim the red light and the wall will become more of a yellow-green. Dim the green light instead, and the wall will become more orange. Bringing up the blue light a bit will cause the orange to become less saturated and more whitish. In all, each setting of the three dimmers will produce a different result, either in color or in brightness or both. The set of all possible results is the gamut defined by those particular color lamps. Swap the red lamp for one of a different brand that is slightly more orange, and there will be a slightly different gamut, since the set of all colors that can be produced with the three lights will be changed.
A computer LCD display can be thought of as a grid of millions of little red, green, and blue lamps, each with their own dimmers. The gamut of the display will depend on the three colors used for the red, green, and blue lights. A wide-gamut display will have very saturated, 'pure' light colors, and thus be able to display very saturated, deep colors.
Applications[edit]
RGB is a convenient color model for computer graphics because the human visual system works in a way that is similar â though not quite identical â to an RGB color space. The most commonly used RGB color spaces are sRGB and Adobe RGB (which has a significantly larger gamut). Adobe has recently developed another color space called Adobe Wide Gamut RGB, which is even larger, in detriment to gamut density.
As of 2007, sRGB is by far the most commonly used RGB color space, particularly in consumer grade digital cameras, HD video cameras, and computer monitors. HDTVs use a similar space, commonly called Rec. 709, sharing the sRGB primaries. The sRGB space is considered adequate for most consumer applications. Having all devices use the same color space is convenient in that an image does not need to be converted from one color space to another before being displayed. However, sRGB's limited gamut leaves out many highly saturated colors that can be produced by printers or in film, and thus is not ideal for some high quality applications. The wider gamut Adobe RGB is being built into more medium-grade digital cameras, and is favored by many professional graphic artists for its larger gamut.
Specifications[edit]
RGB spaces are generally specified by defining three primary colors and a white point. In the table below the three primary colors and white points for various RGB spaces are given. The primary colors are specified in terms of their CIE 1931 color space chromaticity coordinates (x,y).
The CIE 1931 color space standard defines both the CIE RGB space, which is an RGB color space with monochromatic primaries, and the CIE XYZ color space, which works like an RGB color space except that it has non-physical primaries that cannot be said to be red, green, and blue.
Adobe Rgb Color GamutSee also[edit]References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=RGB_color_space&oldid=917621425'
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