<p>There is a diagram on <a href="http://upload.wikimedia.org/wikipedia/commons/8/8d/Diagram_of_the_opponent_process.png" rel="nofollow">wikipedia</a> that is part of the article on the <a href="http://upload.wikimedia.org/wikipedia/commons/8/8d/Diagram_of_the_opponent_process.png" rel="nofollow">opponent process</a>. I assume practical equations have been developed, at least reasonable approximations, but they appear to be missing from the diagram.</p>

<p>There is a quanitity C1 that comes from the L and M cones, and is supposed to represent red minus green. There is a quantity C2 - C3 that comes from all three cone types. If C1 is positive it is a red hue, otherwise green. If C2-C3 is positive it is a yellow hue, otherwise blue.</p>

<p>However actual equations for C1 in terms of cone responses, or for C2-C3 in terms of cone responses, or for A (Brightness) in terms of all three cones <em>and</em> the rod responses are completely missing.</p>

<p>As a related question, that should possibly be separated (let me know if it needs to be a new question):</p>

<p>While RGB defined color can vary with the display device, it would be very useful to have a rough approximation that turns an typical 3 byte RGB triple into a triple of approximate cone and rod responses along with a model of cone and rod saturation (i.e. as you stare at a point how does the cone response change over time). I am sure this has been done and is well known in the right places. Could you point me to it?</p>

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Source for turning cone cell opponent process diagram into equations
John Robertson
# Source for turning cone cell opponent process diagram into equations

(Asked by: username_0 on 2013-06-21)

There is a diagram on [wikipedia](http://upload.wikimedia.org/wikipedia/commons/8/8d/Diagram_of_the_opponent_process.png) that is part of the article on the [opponent process](http://upload.wikimedia.org/wikipedia/commons/8/8d/Diagram_of_the_opponent_process.png). I assume practical equations have been developed, at least reasonable approximations, but they appear to be missing from the diagram.

There is a quanitity C1 that comes from the L and M cones, and is supposed to represent red minus green. There is a quantity C2 - C3 that comes from all three cone types. If C1 is positive it is a red hue, otherwise green. If C2-C3 is positive it is a yellow hue, otherwise blue.

However actual equations for C1 in terms of cone responses, or for C2-C3 in terms of cone responses, or for A (Brightness) in terms of all three cones *and* the rod responses are completely missing.

As a related question, that should possibly be separated (let me know if it needs to be a new question):

While RGB defined color can vary with the display device, it would be very useful to have a rough approximation that turns an typical 3 byte RGB triple into a triple of approximate cone and rod responses along with a model of cone and rod saturation (i.e. as you stare at a point how does the cone response change over time). I am sure this has been done and is well known in the right places. Could you point me to it?

**Tags:** vision, color


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## 0 answers

