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| native_name_lang = en
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| caption = The [[CIE 1931 color space#
| status = Published
| year_started = 1997
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The '''Adobe RGB (1998) color space''' or '''opRGB''' is a [[color space]] developed by [[Adobe
==Historical background==
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Lead developer of Photoshop, [[Thomas Knoll]] decided to build an ICC profile around specifications he found in the documentation for the [[Society of Motion Picture and Television Engineers|SMPTE]] 240M standard, the precursor to [[Rec. 709]] (but not in primaries: 240M also defined EOTF and thus was display referred, sRGB was created by connecting BT.470 PAL and SMPTE C). SMPTE 240M's gamut is wider than that of the BT.709 gamut and the same as BT.470 NTSC (System B, G). 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 (in a special annex to the standard).{{Failed verification|date=February 2021}} 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.{{Dubious|date=February 2021}} On the other hand red and blue primary are the same as in PAL and green is the same as in [[NTSC#Colorimetry|NTSC 1953
Adobe tried numerous tactics to correct the profile, such as correcting the red primary and changing the white point to match that of the [[Standard illuminant#Illuminant series D|CIE Standard Illuminant D50]] (though that will also change the primaries and is thus pointless), 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 [[trademark infringement|infringement]].<ref name = HistoryOfAdobeRGB>{{cite web |url = http://www.realtimerendering.com/blog/2011-color-and-imaging-conference-part-vi-special-session/ |title = 2011 Color and Imaging Conference, Part VI: Special Session |date = 21 December 2011 |website = Real-Time Rendering}}</ref>
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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 [[chromaticity|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 [[candela|cd]]/m<sup>2</sup> at the white point, and 0.5557 cd/m<sup>2</sup> 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.<ref name = AdobeRGBColorImagingEncoding>{{cite
As with sRGB, the ''RGB'' component values in Adobe RGB (1998) are not proportional to the luminances. Rather, a [[gamma correction|gamma]] of approximately 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%.<ref name=InformationDisplayDecember2012SuperHi-Vision>{{cite journal |
The chromaticities of the primary colors and the white point, both of which correspond to the CIE Standard Illuminant D65, are as follows:<ref name=AdobeRGBColorImagingEncoding />
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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 [[color depth|bit depth]]. Color spaces with larger gamuts "stretch" the bits over a broader region of colors, whereas smaller gamuts concentrate these [[bit]]s 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.<ref name = sRGBVsAdobeRGB/> On the contrary, one may have plenty of "spare" bits if using a [[16-bit color|16-bit]] image, thus negating any reduction due to the choice of working space.
==See also==
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==External links==
*[https://web.archive.org/web/20050505000309/http://www.adobe.com/products/adobemag/archive/pdfs/98auhtbf.pdf ''Adobe Magazine'' discussion of Photoshop 5.
*[https://www.adobe.com/digitalimag/adobergb.html Adobe RGB (1998) Color Image Encoding]
*[https://www.eizoglobal.com/library/management/management/03.html Color Management in Practice – Advantages of the Adobe RGB Color Space]
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