ProPhoto RGB color space

ProPhoto RGB

Reference Output Medium Metric RGB
imaginary colors .
Abbreviation	ROMM RGB
Native name	Reference Output Medium Metric RGB ISO 22028-2:2013[1] ANSI/I3A IT10.7666-2002[2]
Status	Published
Latest version	2013 April 2013; 11 years ago (2013-04)[1]
Organization	Kodak IEC ANSI
Committee	ISO/TC 42 (TC) RGB
Domain	Color space, color model
Website	ISO: www.iso.org/standard/56591.html ANSI: webstore.ansi.org/Standards/I3A/ANSII3AIT1076662002

chromaticity diagram

The ProPhoto RGB color space, also known as ROMM RGB (Reference Output Medium Metric), is an output referred

that do not exist and are not visible colors.

When working in color spaces with such a large gamut, it is recommended to work in 16-bit color depth to avoid posterization effects. This will occur more frequently in 8-bit modes as the gradient steps are much larger.

There are two corresponding scene space color encodings known as RIMM RGB (Reference Input Medium Metric) intended to encode standard dynamic range scene space images, and ERIMM RGB intended to encode extended dynamic-range scene space images.^[5][6]

Development

The development of ProPhoto RGB and other color spaces is documented in an article^[7] summarizing a presentation by one of its developers Geoff Wolfe at Kodak, now senior research manager at Canon Information Systems Research Australia, at the IS&T/SPIE Color Imaging Conference in 2011.

Encoding primaries

Color	CIE x	CIE y	CIE X	CIE Y	CIE Z
red	0.734699	0.265301	0.79767	0.28804	0.00000
green	0.159597	0.840403	0.13519	0.71188	0.00000
blue	0.036598	0.000105	0.03134	0.00009	0.82491
white	0.345704	0.358540	0.96420	1.00000	0.82489

Viewing environment

• Luminance level is in the range of 160–640 cd/m².
• Viewing surround is average.
• There is 0.5–1.0% viewing flare.
• The adaptive white point is specified by the chromaticity values for CIE Standard illuminant D50 (${\displaystyle x=0.345704}$, ${\displaystyle y=0.358540}$).
• The image color values are assumed to be encoded using flareless (or flare corrected) colorimetric measurements based on the CIE 1931
  Standard Colorimetric Observer
  .

Encoding function

${\displaystyle X'_{\mathrm {ROMM} }=I_{\mathrm {MAX} }\cdot {\begin{cases}0;&X_{\mathrm {ROMM} }<0.0\\16\cdot X_{\mathrm {ROMM} };&0.0\leq X_{\mathrm {ROMM} }<E_{t}\\X_{\mathrm {ROMM} }^{1/1.8};&E_{t}\leq X_{\mathrm {ROMM} }<1.0\\1;&X_{\mathrm {ROMM} }\geq 1.0\end{cases}}}$

where

${\displaystyle X=R,\,G,\,or\,B}$

and

${\displaystyle I_{\mathrm {MAX} }}$ is the maximum integer value used in the encoding function (e.g. 255 for 8-bit configuration)

and

${\displaystyle E_{t}=16^{1.8/(1-1.8)}=2^{-9}=1/512=0.001953125}$

References

External links

• Specification of ROMM RGB
• Information page about ROMM RGB including a downloadable ICC format profile.
• Understanding ProPhoto RGB
• Color Spaces: Beyond Adobe RGB
• Why Use the ProPhoto RGB Color Space?