LMS color space



LMS is a color space represented by the response of the three types of cones of the human eye, named after their responsivity (sensitivity) at long, medium and short wavelengths.

It is common to use the LMS color space when performing chromatic adaptation (estimating the appearance of a sample under a different illuminant).

XYZ to LMS
Typically, the color to be adapted will be specified in a color space other than LMS, but easily convertible to XYZ. The chromatic adaptation matrix in the von Kries transform method, however, is diagonal in LMS space, thus the usefulness of a transformation matrix M between spaces. The transformation matrices for some chromatic adaptation models in terms of CIEXYZ coordinates are presented here.


 * Notes :
 * All tristimulus values are normally calculated using the CIE 1931 2° standard colorimetric observer..
 * Unless specified otherwise, M is normalized (the rows add up to unity) so the tristimulus values for an equal-energy illuminant (X=Y=Z), like CIE Illuminant E, produce equal LMS values.

CMCCAT97
The CMCCAT97 color appearance model uses the Bradford transformation matrix (MB):

$$ \begin{bmatrix} L\\M\\S \end{bmatrix} = \begin{bmatrix} 0.8951 & 0.2664 & -0.1614 \\ -0.7502 & 1.7135 & 0.0367 \\ 0.0389 & -0.0685 & 1.0296 \end{bmatrix} \begin{bmatrix} X\\Y\\Z \end{bmatrix} $$

RLAB
The RLAB color appearance model uses the Hunt-Pointer-Estevez (HPE) transformation matrix (MH) for conversion from CIE XYZ to LMS:

CAT97s
CIECAM97s uses a spectrally-sharpened Bradford chromatic adaptation matrix:

$$ \begin{bmatrix} L\\M\\S \end{bmatrix} = \begin{bmatrix} 0.8562 & 0.3372 & -0.1934 \\ -0.8360 & 1.8327 & 0.0033 \\ 0.0357 & -0.0469 & 1.0112 \end{bmatrix} \begin{bmatrix} X\\Y\\Z \end{bmatrix} $$

CAT02
The chromatic adaptation matrix (MCAT02) from the CIECAM02 model is:

$$ \begin{bmatrix} L\\M\\S \end{bmatrix} = \begin{bmatrix} 0.7328 & 0.4296 & -0.1624\\ -0.7036 & 1.6975 & 0.0061\\ 0.0030 & 0.0136 & 0.9834 \end{bmatrix} \begin{bmatrix} X\\Y\\Z \end{bmatrix} $$