Editing Color balance (section)

===Von Kries's method===
[[Johannes von Kries]], whose theory of [[rod cell|rods]] and three color-sensitive [[cone cell|cone]] types in the [[retina]] has survived as the dominant explanation of color sensation for over 100 years, motivated the method of converting color to the [[LMS color space]], representing the effective stimuli for the Long-, Medium-, and Short-wavelength cone types that are modeled as adapting independently.  A 3x3 matrix converts RGB or XYZ to LMS, and then the three LMS primary values are scaled to balance the neutral; the color can then be converted back to the desired final [[color space]]:<ref name=Sharma>{{Cite book| title = Digital Color Imaging Handbook | author =  Gaurav Sharma| url = https://books.google.com/books?id=AkByHKRGTsQC&q=%22von+Kries%22&pg=PA153 | publisher = [[CRC Press]] | year = 2003 | isbn = 978-0-8493-0900-7 | page=153 }}</ref>

:<math>\left[\begin{array}{c} L \\ M \\ S \end{array}\right]=\left[\begin{array}{ccc}1/L'_w & 0 & 0 \\ 0 & 1/M'_w & 0 \\ 0 & 0 & 1/S'_w\end{array}\right]\left[\begin{array}{c}L' \\ M' \\ S' \end{array}\right]</math>
where <math>L</math>, <math>M</math>, and <math>S</math> are the color-balanced LMS cone tristimulus values; <math>L'_w</math>, <math>M'_w</math>, and <math>S'_w</math> are the tristimulus values of an object believed to be white in the un-color-balanced image, and <math>L'</math>, <math>M'</math>, and <math>S'</math> are the tristimulus values of a pixel in the un-color-balanced image.

Matrices to convert to LMS space were not specified by von Kries, but can be derived from CIE color matching functions and LMS color matching functions when the latter are specified; matrices can also be found in reference books.<ref name=Sharma/>