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ProPhoto RGB color space

Photographic color space developed by Kodak

Field	Value
title	ProPhoto RGB
long_name	Reference Output Medium Metric RGB
native_name	{{Plainlist
* ISO 22028-2:2013<ref name	"standard-iso"
* ANSI/I3A IT10.7666-2002<ref name	"standard-ansi"
native_name_lang	en
image	CIExy1931 ProPhoto.svg
caption	CIE 1931 xy chromaticity diagram showing the chromaticities enclosed by the ProPhoto RGB color space and location of the primaries. The D50 white point is shown in the center. The areas of the triangle that are outside the colored area are imaginary colors.
status	Published
year_started
first_published
version	2013
version_date
organization	{{Plainlist
committee	ISO/TC 42 (TC)
authors	Kodak
base_standards	RGB
abbreviation	ROMM RGB
domain	Color space, color model
website	{{Plainlist

Reference Output Medium Metric RGB
ISO 22028-2:2013
ANSI/I3A IT10.7666-2002
Kodak
IEC
ANSI
ISO:
ANSI:

The ProPhoto RGB color space, also known as ROMM RGB (Reference Output Medium Metric), is an output referred RGB color space developed by Kodak. It offers an especially large gamut designed for use with photographic output in mind. The ProPhoto RGB color space encompasses over 90% of possible surface colors in the CIE Lab* color space, and 100% of likely occurring real-world surface colors documented by Michael Pointer in 1980, making ProPhoto even larger than the Wide-gamut RGB color space. The ProPhoto RGB primaries were also chosen in order to minimize hue rotations associated with non-linear tone scale operations. One of the downsides to this color space is that approximately 13% of the representable colors are imaginary colors 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.

Development

The development of the ProPhoto RGB and other color spaces is documented in an article summarizing a presentation by one of its developers Geoff Wolfe at Kodak, currently 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 (x = 0.345704, 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

: X'\mathrm{ROMM} = I\mathrm{MAX} \cdot \begin{cases} 0; & X_\mathrm{ROMM} \end{cases}

where

:X = R,, G,, or, B

and

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

and

:E_t = 16^{1.8/(1-1.8)} = 2^{-9} = 1/512 = 0.001953125

References

ISO. (April 2013). "ISO - ISO 22028-2:2013 - Photography and graphic technology — Extended colour encodings for digital image storage, manipulation and interchange — Part 2: Reference output medium metric RGB colour image encoding (ROMM RGB)".
International Imaging Industry Association. (2002). "ANSI/I3A IT10.7666-2002 - Photography - Electronic Still Picture Imaging - Reference Output Medium Metric RGB Color Encoding (ROMM-RGB)".
Pointer, M. R.. (1980). "The Gamut of Real Surface Colours. Color Res. Appl., 5". Color Research & Application.
(2014-02-19). "The Pointer's Gamut - The coverage of real surface colors by RGB color spaces and wide gamut".
ISO. (August 2012). "ISO - ISO/TS 22028-3:2012 - Photography and graphic technology — Extended colour encodings for digital image storage, manipulation and interchange — Part 3: Reference input medium metric RGB colour image encoding (RIMM RGB)".
International Imaging Industry Association. (2002). "ANSI/I3A IT10.7466-2002 - Photography - Electronic still picture imaging - Reference Input Medium Metric RGB Color encoding (RIMM-RGB)".
Naty. (2011-12-21). "Real-Time Rendering · 2011 Color and Imaging Conference, Part VI: Special Session".

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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