ProPhoto RGB color space

The ProPhoto RGB color space, also known as ROMM RGB, 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 L*a*b* 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.

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==

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==

Encoding function

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

Source: Wikipedia ↗

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