Consequences of photoreceptor anomalies
As we have considered, the process of colour vision begins with the summarisation of the light spectrum by the cone photoreceptors. If there anomalies in such photoreceptors (where 'anomaly' is relative to the human population), this can have flow-on effects on colour vision.
Rarely, such anomalies can take the form of missing one or more of the classes of cone photoreceptor (for example, having no 'L' cones). A far more common anomaly is where the three cone classes are present but one or more of them have differences in their sensitivity profile.
One such anomaly is called 'protanomaly', and occurs when the sensitivity of the 'L' cones is shifted across such that it is close to the sensitivity of the 'M' cones. This is a form of what is known colloquially as 'red-green colour blindness'.
Here, we will look at a coarse simulation of protanomaly in which the sensitivity of the 'L' cones is changed to match that of the 'M' cones. The below shows the perceptual representation obtained from these photoreceptors.
Discriminability estimates
We can also look at discriminability under protanomaly. As previously, you can click on a pixel in the scene image above and the image below will show how perceptually discriminable that pixel is from the rest of the scene (with increasing brightness corresponding to increased discriminability).