View source for SRGB

{{short description|Standard RGB color space}}
{{For|the ancillary chunk in the PNG file format|PNG#Ancillary chunks}}
{{Lowercase title}}
{{Infobox technology standard
| title = sRGB
| long_name = IEC 61966-2-1 Default RGB Colour Space - sRGB
| native_name_lang = English
| image = SRGB chromaticity CIE1931.svg
| caption = sRGB colors situated at calculated position in {{tooltip|[[CIE 1931 color space|CIE 1931]] chromaticity diagram|edited from File:CIExy1931_sRGB.svg}}. Luminance <math>Y</math> set so that <math>R+G+B = 1</math> to avoid [[mach bands]].
| status = Published
| year_started = 1996
| first_published = {{Start date and age|1999|10|18}}<ref name=IEC1999/>
| version = 
| version_date = 
| preview = 
| preview_date = 
| organization = {{abbr|[[International Electrotechnical Commission|IEC]]|International Electrotechnical Commission}}<ref name=IEC1999/>
| committee = '''{{abbr|TC|Technical Committee}}'''/'''{{abbr|SC|Sub-committee}}''': TC 100/TA 2<ref name=IEC1999/>
| editors = 
| authors = 
| base_standards = IEC 61966 Colour Measurement and Management in Multimedia Systems and Equipment
| related_standards = 
| abbreviation = sRGB
| domain = [[Color space]], [[color model]]
| license = 
| website = {{URL|https://webstore.iec.ch/publication/6169}}
}}

'''sRGB''' is a standard numerical encoding of colors, based on the [[RGB color spaces|RGB (red, green, blue) color model]], for use on monitors, printers, and the [[World Wide Web]]. It was initially proposed by [[Hewlett-Packard|HP]] and [[Microsoft]] in 1996<ref name=IEC1996draft/> and became an official standard of the [[International Electrotechnical Commission]] (IEC) as IEC 61966-2-1:1999.<ref name=IEC1999/> It is the current defined standard [[colorspace]] for the web, and it is usually the assumed colorspace for images that are neither tagged for a colorspace nor have an [[ICC profile|embedded color profile]].

The sRGB standard uses the same color primaries and white point as the [[Rec. 709|ITU-R BT.709]] standard for [[high-definition television|HDTV]],<ref name=poyn2003/> but a different [[transfer functions in imaging|transfer function]] (or [[gamma correction|gamma]]) compatible with the era's [[CRT display]]s,<ref name=ImEn2012/> and assumes a viewing environment closer to typical home and office viewing conditions.

The sRGB color space is also the basis of the '''[[sYCC]]''' color encoding, which is a remapping of the R, G, and B components of sRGB to a luminance (brightness) value <math>Y</math> and two [[chroma channel]]s similar to those of the [[CIE 1931 color space|CIE]] [[YCbCr]] encoding.<ref name=IEC2003/>

== sRGB definition ==

===Gamut===
{| class="wikitable floatright"
|-
! [[CIE 1931 color space#CIE xy chromaticity diagram and the CIE xyY color space|Chromaticity]]
! Red
! Green
! Blue
! White point
|-
| ''x''
| 0.6400
| 0.3000
| 0.1500
| 0.3127
|-
| ''y''
| 0.3300
| 0.6000
| 0.0600
| 0.3290
|-
| ''Y''
| 0.2126
| 0.7152
| 0.0722
| 1.0000
|}

The sRGB standard defines the [[chromaticity|chromaticities]] of the red, green, and blue [[primary color|primaries]], the colors where one of the three channels is nonzero and the other two are zero. The [[gamut]] of chromaticities that can be represented in sRGB is the [[color triangle]] defined by these primaries, which are set such that the range of colors inside the triangle is well within the range of colors visible to a human with normal [[Trichromacy|trichromatic]] vision. As with any [[RGB color space]], for non-negative values of R, G, and B it is not possible to represent colors outside this triangle.

The primaries come from HDTV ([[Rec. 709|ITU-R BT.709]]), which are somewhat different from those for older color TV systems ([[Rec. 601|ITU-R BT.601]]). These values were chosen to reflect the approximate color of consumer CRT phosphors at the time of its design. Since [[flat-panel display]]s at the time were generally designed to emulate CRT characteristics, the values also reflected prevailing practice for other display devices as well.<ref name=IEC1999/>

=== Transfer function ("gamma") ===
[[File:SRGB gamma.svg|thumb|Plot of the sRGB intensities (red), and this function's slope in log-log space (blue), which is the instantaneous gamma. Below a compressed value of 0.04045 or a linear intensity of 0.00313, the curve is linear so the gamma is 1. Behind the red curve is a dashed black curve showing an exact gamma = 2.2 power law.]]

[[File:srgbnonlinearity.png|thumb|On an sRGB display, each solid bar should look as bright as the surrounding striped dither. (Note: must be viewed at original, 100% size)]]

The sRGB standard specifies a non-linear encoding of physical brightness values (proportional to luminous [[power (physics)|power]] emitted per unit of area) into the integer R, G, and B values that are to be stored in computer memory or [[image file]]s. This [[transfer functions in imaging|transfer function]] commonly called '''gamma encoding''', is the combination of a [[linear function]] at low brightness values and a displaced [[power law]] for the rest of the range.

Specifically, let <math>z</math> be the encoded R, G, or B value, assumed to be an integer ranging from 0 (meaning no light) to some maximum <math>M</math> (meaning the maximum displayable intensity of that channel). Typically <math>M</math> is 255 when <math>z</math> as an 8-bit integer, or generally <math>2^N - 1</math> for an <math>N</math>-bit integer. The physical intensity represented by <math>z</math> is defined as <math>v = D(z/M)</math>, where the decoding function <math>D</math> is defined as<ref name=IEC2003/>
:<math>D(u) = \begin{cases}
u/12.92, & u \le 0.04045 \\[5mu]
\left(\frac{\displaystyle u + 0.055}{\displaystyle 1.055}\right) ^{2.4}, & u > 0.04045
\end{cases}</math>
The result is 0 for no light, and 1 for the maximum intensity. The value <math>v = D(z/M)</math> is sometimes called the "linear value" or "linear-light value" corresponding to the encoded sample <math>z</math>.


Conversely, given a value <math>v</math> between 0 and 1 that is proportional to the physical R, G, or B intensity to be displayed, the encoded integer intensity will be <math>z = \mbox{round}(M E(v))</math>, where encoding function <math>E</math> is defined as<ref name=IEC2003/>
:<math>E(v) = \begin{cases}
12.92 v, & v \le 0.0031308 \\[5mu]
(1.055)v^{1/2.4} - 0.055, & v > 0.0031308
\end{cases}</math>


These sRGB encoding and decoding functions <math>D</math> and <math>E</math> above are similar in form to those of BT.709, but the values are noticeably different.<ref name=ImEn2012/> Because of the rounding of the parameters, they have small discontinuities at the transition between the linear and non-linear part, on the order of 10<sup>−8</sup> — which are too small to matter in most practical situations.<ref name=summ2012/>

For medium and large values of the argument <math>u</math>, the decoding function <math>D</math> is actually quite close to a pure power law with exponent (gamma) of 2.2. However, for low values (around and below the breakpoint <math>U</math>) the difference is perceptible.<ref name=ImEn2012/><ref name=sira2020/>

If needed, the encoding and decoding functions <math>D</math>, <math>E</math> can be used for arguments greater than 1. They are also extended to negative values by the identities <math>D(-u) = -D(u)</math>, <math>E(-v) = -E(v)</math>.<ref name=IEC2003/>

In practice, there is still debate and confusion about the formulas used for encoding and decoding image colors from or into "sRGB" files.<ref name=hard2001/> Also, programmers may choose use the "pure" power law <math>D(u) =u^{2.2}</math> instead of the correct piecewise formulas above, for the sake of code simplicity or efficiency, but that would introduce some issues near black. Also, some operating systems and programs may directly send sRGB encoded images to monitors which actually have a different effective decoding function, such as pure power law with 2.2 exponent, this is further complicated by the standard saying that reference CRT display should use 2.2 gamma.<ref name=sira2020/>

===Correspondence to CIE XYZ stimulus===

The sRGB standard specifies also the colors and relative intensities of the three primaries R, G, and B, by defining the mapping between these values (in linear brightness scale, before the gamma encoding) and the [[CIE 1931 color space|CIE XYZ]] perceptual color coordinates.<ref name=lindNNNN/> This mapping is the same specified by the BT.709 standard; in matrix notation,<ref name=IEC2003/>

:<math>
\begin{bmatrix} X_{D65} \\ Y_{D65} \\ Z_{D65} \end{bmatrix}
=
\begin{bmatrix}
 0.4124 & 0.3576 & 0.1805 \\
 0.2126 & 0.7152 & 0.0722 \\
 0.0193 & 0.1192 & 0.9505
\end{bmatrix}
\begin{bmatrix} R_\text{linear} \\ G_\text{linear} \\ B_\text{linear} \end{bmatrix}
</math>

These coefficients should be considered exact<ref name=IEC1999/> and assume the 2° [[standard colorimetric observer]] for CIE XYZ.<ref name=IEC1996draft/><ref name=ICC2015/> In particular, the second row of this matrix specifies the computation of the [[YCbCr#ITU-R BT.709 conversion|BT.709-2 luma (brightness) value]] from the linear R, G, and B values. (BT.709-1 had a typo in these coefficients.)

The inverse conversion, from from CIE XYZ to (linear) sRGB, can be obtained by inverting the matrix above to a suitable numerical accuracy. The 1999 standard provides the matrix
:<math>
\begin{bmatrix} R_\text{linear} \\ G_\text{linear} \\ B_\text{linear} \end{bmatrix}
= \begin{bmatrix}
 +3.2406 & -1.5372 & -0.4986 \\
 -0.9689 & +1.8758 & +0.0415 \\
 +0.0557 & -0.2040 & +1.0570
\end{bmatrix}
\begin{bmatrix} X_{D65} \\ Y_{D65} \\ Z_{D65} \end{bmatrix}
</math>
which is not the exact inverse of the sRGB to XYZ transformation, but was expected to be accurate enough for 8-bit encoded samples (with <math>M=255</math>).

The 2003 amended version of the sRGB standard<ref name=IEC2003/> points out that higher accuracy is needed when the samples are encoded with more than 8 bits. It provides the matrix
:<math>
\begin{bmatrix} R_\text{linear} \\ G_\text{linear} \\ B_\text{linear} \end{bmatrix}
= \begin{bmatrix}
 +3.2406255 & -1.5372080 & -0.4986286 \\
 -0.9689307 & +1.8757561 & +0.0415175 \\
 +0.0557101 & -0.2040211 & +1.0569959
\end{bmatrix}
\begin{bmatrix} X_{D65} \\ Y_{D65} \\ Z_{D65} \end{bmatrix}
</math>.
which is claimed to be sufficiently accurate for samples with <math>N=16</math> bits (<math>M = 65535</math>).

For these formulas, the ''X'', ''Y'', and ''Z'' values must be scaled so that the ''Y'' of [[Illuminant D65|D65]] ("white") is 1.0 (''X'' = 0.9505, ''Y'' = 1.0000, ''Z'' = 1.0890). This is usually true but some color spaces use 100 or other values (such as in [[CIELAB color space#Forward transformation|CIELAB]], when using specified white points).

=== Viewing environment ===
[[File:Cie Chart with sRGB gamut by spigget.png|thumb|CIE 1931 xy [[chromaticity diagram]] showing the [[gamut]] of the sRGB color space (the triangle). The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers (labeled in blue). This image is drawn using sRGB, so colors outside the triangle cannot be accurately colored and have been interpolated. The [[Illuminant D65|D65]] [[white point]] is shown in the center, and the [[Planckian locus]] is shown with color temperatures labeled in [[kelvin]]s. D65 is not an ideal 6504-kelvin [[black body]] because it is based on atmospheric filtered daylight.]]

The sRGB specification assumes a dimly lit encoding (creation) environment with an ambient correlated color temperature (CCT) of 5003 K:
{| class="wikitable" style="margin-right: 20px;"
|-
! Parameter
! Value
|-
| Screen [[luminance]] level
| 80&nbsp;cd/m<sup>2</sup>
|-
| Illuminant [[white point]]
| ''x'' = 0.3127, ''y'' = 0.3290 ([[Illuminant D65|D65]])
|-
| Image surround reflectance
| 20% (~medium gray)
|-
| Encoding ambient illuminance level
| 64 [[lux]]
|-
| Encoding ambient white point
| ''x'' = 0.3457, ''y'' = 0.3585 ([[Standard illuminant#Illuminant series D|D50]])
|-
| Encoding viewing flare
| 1.0%
|-
| Typical ambient illuminance level
| 200 lux
|-
| Typical ambient white point
| ''x'' = 0.3457, ''y'' = 0.3585 (D50)
|-
| Typical viewing flare
| 5.0%
|}
The assumed ambient CCT differs from that of the BT.709 standard illuminant ([[Illuminant D65|D65]]), which is still retained for the screen white point. Using [[Standard illuminant#Illuminant series D|D50]] for both would have made the white point of most photographic paper appear excessively blue.<ref name=rodn2005/><ref name=XritPPPP/> The other parameters, such as the luminance level, are representative of a typical CRT monitor.

For optimal results, the [[International Color Consortium|ICC]] recommends using the encoding viewing environment (i.e., dim, diffuse lighting) rather than the less-stringent typical viewing environment.<ref name=ICC.sRGB/>

==The bg-sRGB space==

Annex G of the 2003 amendment of the sRGB standard describes an alternative encoding of color values, called '''bg-sRGB''', that is recommended when the number of bits per channel <math>N</math> is 10 or more.

In this alternative encoding, an integer encoded sample value <math>z</math> and the corresponding linear R, G, or B value <math>v</math> are related by the formulas
:<math>v = D\left(\frac{\displaystyle z - K}{\displaystyle W - K}\right)</math>
and
:<math>z = \mbox{round}(K + (W-K)E(v))</math> 
where the <math>D</math> and <math>E</math> functions are the same as in the sRGB space. The standard specifies <math>K = 384</math> and <math>W = 894</math> for <math>N=10</math>, and generally 
:<math> K = 3\times 2^{N-3}\quad\quad W = K + 255\times 2^{N-9}</math> 
for <math>N>10</math>.
In the bg-sRGB color space, the null intensity <math>v=0</math> is encoded as the integer <math>K</math>, and the maximum displayable intensity <math>v=1</math> is encoded as the integer <math>W</math>. This encoding is useful for color space manipulations (like the conversion from sYCC) that can generate values <math>v</math> that are negative or greater than 1.<ref name=IEC2003/>

==History==

The non-linear encoding of physical data samples is a common [[digital signal processing]] technique that aims to make better use of the bits available for the encoded signal, taking into account the non-linear way human senses perceive physical stimuli. Using smaller increments for smaller signals reduces the [[quantization (image processing)|quantization]] artifacts.

This principle was incorporated into the digital-to-analog converters and the analog circuitry of early computer monitors, resulting in an effective [[transfer functions in imaging|decoding function]] (the mapping from digital sample values to the displayed intensity) which was roughly a power law with an exponent between 2 and 3. The exponent was commonly denoted with the letter <math>\gamma</math>, hence the common name "gamma correction" (or similar) for this function. This mapping initially varied according to CRT manufacturers, but was normalized in 1993 for use in HDTV systems, as the [[ITU]] [[Rec. 709|BT.709]] standard<ref name=ITU1993.709/> The BT.709 standard specified a decoding function with a linear section near zero, transitioning to a shifted power law with exponent 1/0.45 ≈ 2.2222....

The sRGB encoding was created a few years later by Hewlett-Packard and Microsoft. It was meant to describe the decoding function of most [[Cathode-ray tube|CRT]] computer monitors used with Windows operating systems at the time, which was still different from that assumed by BT.709.<ref name=HPWWWW/> The first draft of the standard <ref name=IEC1996draft/> was published in 1996. A fourth draft, still incomplete, is available online.<ref name=IEC1966-4/> Like the BT.709, the sRGB decoding function was defined as a linear section near zero that transitions to a shifted power law <ref name=robe1991/><ref name=colo2015/>

=== Justification for the formulas ===

In theory, the parameters of the encoding and decoding functions should be chosen so that the transition from the linear section to the power law section is [[continuous function|continuous]] (without a sudden step) and [[smooth function|smooth]] (without a sudden change of slope).<ref name=HPWWWW/>

To derive the decoding function, one considers that the general formula for a linear function, whose graph is a straight line that passes through {{math|(0,0)}}, is <math>y = x/A</math>, and a shifted power law curve that passes through {{math|(1,1)}} is <math>y = \left(\frac{x+C}{1+C}\right)^\Gamma</math>

To obtain a seamless transition between the two functions when <math>x</math> has a value <math>U</math>, we must have

:<math>\frac{x}{A} = \left(\frac{U+C}{1+C}\right)^\Gamma</math>

To avoid a sudden change of slope where the two segments meet, the derivatives must be equal at this point:

:<math>\frac{1}{A} = \Gamma\left(\frac{U+C}{1+C}\right)^{\Gamma-1}\left(\frac{1}{1+C}\right)</math>

Solving the two equations for <math>U</math> and <math>A</math> we get
:<math>U = \frac{C}{\Gamma-1}\;\;\;\;\; A = \frac{(1+C)^\Gamma(\Gamma-1)^{\Gamma-1}}{(C^{\Gamma-1})(\Gamma^\Gamma)}</math>

=== Parameter values ===

The first draft of the sRGB standard<ref name=IEC1996draft/> initially set the parameters at <math>C = 0.055</math> and <math>\Gamma= 2.4</math> so that the resulting decoding function <math>D</math> closely resembled a pure [[gamma correction|power law]] with exponent (gamma) 2.2, assimed to be typical of computer monitors at the time. This choice implies a breakpoint <math>U \approx 0.0392857...</math> and a linear coefficient <math>A \approx 12.9232102...</math>. These values, rounded to <math>U = 0.03928</math> and <math>A = 12.92321</math> are still incorrectly given in some publications.<ref name=gree2002/> However, the value of <math>A</math> was rounded to <math>12.92</math> already in the sRGB draft standard,<ref name=IEC1996draft/> resulting in a small discontinuity in the curve.

The first official version of the standard was defined and published by the IEC in 1999. In this version, the rounded value of <math>A =12.92 </math> was retained, but the breakpoint <math>U</math> was redefined as <math>0.04045</math> to make the curve approximately continuous. With these values, there is still a discontinuity in the slope, from <math>1/12.92</math> just below the intersection to <math>1/12.70</math> just above it. The final standard also corrected some small rounding errors present in the draft.<ref name=IEC1996draft/>

The 1999 IEC standard was amended in 2003.<ref name=IEC2003/> The sRGB to CIE XYZ matrix was retained, but the inverse transformation above was replaced by a more accurate version, with seven decimal fraction digits. The amended standard also included the definition of the sYCC encoding, using brightness (Y) and two [[Chrominance|chroma]] coordinates (CC) instead of R, G, and B coordinates, and a bg-sRGB encoding for 10-bit components which allows some component values outside the 0-1 range.

==Usage==
[[File:CIE1931xy gamut comparison.svg|thumb|upright=1.16|Comparison of some RGB and CMYK colour gamuts on a [[CIE 1931]] xy [[chromaticity diagram]]]]

Due to the standardization of sRGB on the Internet, on computers, and on printers, many low- to medium-end consumer [[digital camera]]s and [[image scanner|scanners]] use sRGB as the [[default (computer science)|default]] (or only available) working color space. However, consumer-level [[charge-coupled device|CCDs]] are typically uncalibrated, meaning that even though the image or device is being labeled as "sRGB", one cannot assume that the encoded values or the colors of displayed images are accurate as specified by the standard. Recently that changed and smartphones and TVs have very good calibration out of the box.

If the color space of an image is unknown and the R, G, and B samples are encoded with 8 bits each, the sRGB encoding usually the assumed default.<!-- See Talk page -->

As the sRGB gamut mostly meets or exceeds the gamut of a low-end [[inkjet printer]], an sRGB image is often regarded as satisfactory for home printing. The sRGB color space is sometimes avoided by high-end print publishing professionals because its color gamut is not big enough, especially in the blue-green colors, to include all the colors that can be reproduced in [[CMYK]] printing. Images intended for professional printing via a fully color-managed workflow (e.g. [[prepress]] output) sometimes use another color space such as [[Adobe RGB color space|Adobe RGB (1998)]], which accommodates a wider gamut and CMYK color space like Fogra39. Such CMYK and sRGB images used on the Internet may be converted to sRGB using [[color management]] tools that are usually included with software that works in these other color spaces.

===Programming interface support===

The two dominant programming interfaces for 3D graphics, [[OpenGL]] and [[Direct3D]], have both incorporated support for the sRGB gamma curve. OpenGL supports [[texture mapping|textures]] with sRGB gamma encoded color components (first introduced with EXT_texture_sRGB extension,<ref name=OpGL2007/> added to the core in OpenGL 2.1) and rendering into sRGB gamma encoded [[framebuffer]]s (first introduced with EXT_framebuffer_sRGB extension,<ref name=OpGL2010/> added to the core in OpenGL 3.0). Correct [[mipmap]]ping and [[interpolation]] of sRGB gamma textures has direct hardware support in texturing units of most modern [[GPU]]s (for example nVidia GeForce 8 performs conversion from 8-bit texture to linear values before interpolating those values), and does not have any performance penalty.<ref name=NVIDZZZZ/>

===ICC profiles===

A [[lookup table]] may be used to efficiently convert sRGB to other color spaces.{{Citation needed|date=December 2024}} The [[International Color Consortium]] (ICC) has published [[ICC profile|color profiles]] for this purpose, which are widely used.<ref name=ICC.sRGB/><ref name=ICC2015/> There are several variants,<ref name=ICC.profs/> including [[ICC profile|ICCmax]], version 4, and version 2.

Version 4 is generally recommended, but version 2 is still commonly used and is the most compatible with other software including browsers.<ref>{{Cite web |title=Is your system ICC Version 4 ready? |url=https://www.color.org/version4html.xalter |access-date=2024-12-21 |website=www.color.org}}</ref> However, inconsistencies have been pointed out between those ICC profiles and the IEC sRGB standard.<ref name=stonQQQQ/> In particular, version 2 of the ICC profile specification does not implement the piecewise parametric curve encoding ("para") as specified by the IEC sRGB standard,<ref>{{Cite web |title=Android lock screen bug and ICC profiles |url=https://color.org/security/android_bug.xalter |access-date=2024-12-25 |website=color.org}}</ref> and has to implement the linear spline using 1DLUT.<ref name=ICC.profs/> What is worse in some cases "simplified sRGB" is used which is just 2.2 gamma.<ref>{{Cite web |last=Developers |first=Colour |date=2019-10-25 |title=sRGB EOTF: Pure Gamma 2.2 Function or Piece-Wise Function? |url=https://www.colour-science.org/posts/srgb-eotf-pure-gamma-22-or-piece-wise-function/ |access-date=2024-12-25 |website=Colour Science |language=en}}</ref>

== The sYCC color space ==
Amendment 1 to IEC 61966-2-1:1999, approved in 2003, includes the definition of a [[YCbCr|Y′Cb′Cr′]] color representation called '''sYCC'''. Although the RGB color primaries are based on BT.709, the equations for transformation from sRGB to sYCC and vice versa are based on [[Rec. 601|BT.601]]. The sYCC standard specifies 8 bits for the encoded components, and the matrices result in a range of approximately 0&ndash;1 for Y; -0.5&ndash;0.5 for C.<ref name=IEC2003/>

As this conversion can result in sRGB values outside the range 0&ndash;1, the amendment describes how to apply the gamma correction to negative values, by applying {{math|−''f''(−''x'')}} when {{mvar|x}} is negative (and {{mvar|f}} is the sRGB↔linear functions described above). This is also used by [[scRGB]].

==References==
{{notelist}}
<references>

<ref name=IEC1996draft>{{cite web|author1=Michael Stokes|author2=Matthew Anderson|author3=Srinivasan Chandrasekar|author4=Ricardo Motta|date=November 5, 1996|title=A Standard Default Color Space for the Internet – sRGB, Version 1.10|url=https://www.w3.org/Graphics/Color/sRGB.html|url-status=live|archive-url=https://web.archive.org/web/20230703221707/https://www.w3.org/Graphics/Color/sRGB.html |archive-date=Jul 3, 2023 |access-date=|website=}}</ref>

<ref name=IEC1966-4>[https://web.archive.org/web/20141225172302/http://www2.units.it/ipl/students_area/imm2/files/Colore1/sRGB.pdf fourth working draft (4WD) for 2CD of IEC 61966-2-1], (archived). Still not the complete standard.</ref>

<ref name=IEC1999>{{cite web|title=IEC 61966-2-1:1999|url=https://webstore.iec.ch/publication/6169|website=IEC Webstore|publisher=International Electrotechnical Commission|access-date=3 March 2017}}. The first official specification of sRGB.</ref>

<ref name=IEC2003>{{cite web |url=https://webstore.iec.ch/publication/6168 |title=IEC 61966-2-1:1999 Multimedia systems and equipment – Colour measurement and management – Part 2-1: Colour management – Default RGB colour space – sRGB: Amendment 1 |date=2003 |publisher=[[International Electrotechnical Commission]]}} Replaces the version IEC 61966-2-1:1999, introducing the sYCC encoding for [[YCbCr]] color spaces, an extended-[[gamut]] RGB encoding bg-sRGB, and a [[CIELAB]] transformation.</ref>

<ref name=poyn2003>{{cite book |title=Digital Video and HDTV: Algorithms and Interfaces |author=Charles A. Poynton |publisher=Morgan Kaufmann |year=2003 |isbn=1-55860-792-7 |url=https://books.google.com/books?id=ra1lcAwgvq4C&q=rec+709+smpte&pg=RA1-PA239}}</ref>

<ref name=gree2002>{{cite book|author1=Phil Green|url=https://books.google.com/books?id=tn09voxr6agC&q=srgb+0.03928+date:0-2002&pg=PA350|title=Colour Engineering: Achieving Device Independent Colour|author2=Lindsay W. MacDonald|publisher=John Wiley and Sons|year=2002|isbn=0-471-48688-4|name-list-style=amp}}</ref>

<ref name=summ2012>Jason Summers (2012): "[https://entropymine.com/imageworsener/srgbformula/ A close look at the sRGB formula]". Online document at entropymine.com. Accessed on 2014-12-17 ([https://web.archive.org/web/20240926160131/https://entropymine.com/imageworsener/srgbformula/ archived])</ref>

<ref name=sira2020>Daniele Siragusano (2020): "[https://www.youtube.com/watch?v=NzhUzeNUBuM Colour Online: sRGB... We Need To Talk]". 
YouTube video of talk (2020-07-17, 57 min) discussing mismatch between sRGB and actual monitor transfer functions. Posted in channel @FilmLight. Accessed on 2024-12-17.</ref>

<ref name=hard2001>{{cite book|author=Jon Y. Hardeberg|url=https://books.google.com/books?id=e2umTIdI2u4C&q=srgb+0.00304+date:0-2002&pg=PA40|title=Acquisition and Reproduction of Color Images: Colorimetric and Multispectral Approaches|publisher=Universal-Publishers.com|year=2001|isbn=1-58112-135-0}}</ref>

<ref name=robe1991>{{cite report|last=Roberts|first=A.|title=BBC RD 1991/6 Methods of Measuring and Calculating Display Transfer Characteristics|url=https://downloads.bbc.co.uk/rd/pubs/reports/1991-06.pdf|publisher=BBC|pages=1}}</ref>

<ref name=colo2015>NumFocus Colour Science (2015): "[https://www.colour-science.org/posts/the-importance-of-terminology-and-srgb-uncertainty/ The Importance of Terminology and sRGB Uncertainty]".  Online document at www.colour-science.org, dated 2015-12-05. Accessed on 2024-12-17 ([https://web.archive.org/web/20241218212521/https://www.colour-science.org/posts/the-importance-of-terminology-and-srgb-uncertainty/ archived]).</ref>

<ref name=ITU1993.709>{{Cite web|url=https://www.itu.int/rec/R-REC-BT.709|title=BT.709 : Parameter values for the HDTV standards for production and international programme exchange|website=www.itu.net|date=n.d.|access-date=2021-04-19}}</ref>

<ref name=OpGL2007>{{cite web |title=EXT_texture_sRGB |date=24 January 2007 |url=https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_texture_sRGB.txt |access-date=12 May 2020}}</ref>

<ref name=OpGL2010>{{cite web |title=EXT_framebuffer_sRGB |date=17 September 2010 |url=https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_framebuffer_sRGB.txt |access-date=12 May 2020}}</ref>

<ref name=NVIDZZZZ>{{cite web |title=GPU Gems 3: Chapter 24. The Importance of Being Linear, section 24.4.1 |publisher=NVIDIA Corporation |url=https://developer.nvidia.com/gpugems/gpugems3/part-iv-image-effects/chapter-24-importance-being-linear |access-date=3 March 2017}}</ref>

<ref name=HPWWWW>[https://web.archive.org/web/20030124233043/http://www.srgb.com/ sRGB.com Notes on design and use of sRGB] (archived) by [[Hewlett Packard|HP]].</ref>

<ref name=ImEn2012>Image Engineering GmbH (2012): "[https://www.image-engineering.de/library/technotes/714-color-spaces-rec-709-vs-srgb Color spaces - REC.709 vs. sRGB] Online document at www.image-engineering.de.  Includes a graph comparing two transfer functions. Accessed on 2024-12-17.</ref>

<ref name=ICC.profs>International Color Consortium (undated): "[https://color.org/srgbprofiles.xalter sRGB profiles]". Summary page at color.org. Accessed on 2014-12-17 (archiving failed).</ref>

<ref name=ICC.sRGB>International Color Consortium (undated): "[https://www.color.org/chardata/rgb/srgb.xalter sRGB]" Summary page at color.org. Accessed on 2014-12-17 (archiving failed).</ref>

<ref name=ICC2015>International Color Consortium (2015): "[https://www.color.org/sRGB.pdf How to interpret the sRGB color space (specified in IEC 61966-2-1) for ICC profiles]".  Online document at www.color.org. Accessed on 2024-12-17 ([https://web.archive.org/web/20241209023511/https://color.org/chardata/rgb/sRGB.pdf archived])</ref>

<ref name=lindNNNN>[http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html Conversion matrices for RGB vs. XYZ conversion] by Bruce Justin Lindbloom</ref>

<ref name=rodn2005>{{cite book |last=Rodney |first=Andrew |url=https://books.google.com/books?id=jFl-3v9sSEUC&q=%22My+suggestion+is+to+calibrate+to+a+D65+white+point.%22&pg=PA121 |title=Color Management for Photographers |publisher=Focal Press |year=2005 |isbn=978-0-240-80649-5 |page=121 |quote=}}</ref>

<ref name=XritPPPP>{{Cite web |title=Why Calibrate Monitor to D65 When Light Booth is D50 |url=https://www.xrite.com/service-support/why_calibrate_monitor_to_d65_when_light_booth_is_d50 |access-date=2022-09-11 |website=X-Rite |language=en}}</ref>

<ref name=stonQQQQ>[https://ninedegreesbelow.com/photography/srgb-profile-comparison.html Will the Real sRGB Profile Please Stand Up?] by Elle Stone.  Analyzes the inconsistency among sRGB ICC profiles</ref>

</references>

==External links==
* [https://www.shadertoy.com/view/7sjBWD Test that shows whether your display is pure 2.2 gamma or sRGB (~2.2 gamma)] on [[Shadertoy]]

{{Color space}}

[[Category:1996 introductions]]
[[Category:Color space]]
[[Category:Film and video technology]]