Editing Opponent process (section)

===Relation to LMS color space===
[[File:Diagram of the opponent process.png|right|thumb|360px|Diagram of the opponent process {{citation needed|date=June 2022}}]]
Though the [[Young–Helmholtz theory|trichromatic]] and opponent processes theories were initially thought to be at odds, the opponent process theory has been refined so as to claim that the mechanisms responsible for the opponent process receive signals from the three types of cones predicted by the [[trichromatic theory]] and process them at a more complex level.<ref name="Kandel">Kandel E. R., Schwartz J. H. and Jessell T. M., 2000. ''Principles of Neural Science'', 4th ed., McGraw–Hill, New York. pp.&nbsp;577–580.</ref>

Most humans have three different [[cone cell]]s in their retinas that facilitate [[trichromacy|trichromatic color vision]]. Colors are determined by the proportional excitation of these three cone types, i.e. their ''quantum catch''. The levels of excitation of each cone type are the parameters that define [[LMS color space]]. To calculate the opponent process [[CIE 1931 color space#Tristimulus values|tristimulus values]] from the LMS color space, the cone excitations must be compared:{{citation needed|date=September 2022}}
* The luminous opponent channel is equal to the sum of all three cone cells (plus the [[rod cell]]s in some conditions).
* The red–green opponent channel is equal to the difference of the L- and M-cones.
* The blue–yellow opponent channel is equal to the difference of the S-cone and the sum of the L- and M-cones.