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We have five types of photo receptors in the eyes but computer color systems just use the three red, green and blue.

Human eye sensitivity

Three could be motivated if rod and melanopsin sensations are just linear combinations of cone sensations. Is it so or would a five color display with two additional pixel components with a frequency distribution similar to that of rods and melanopsin respectively add image quality?

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  • $\begingroup$ This is a very interesting question, but I'm not sure it is on-topic here. $\endgroup$
    – Yuval Filmus
    Jan 21 at 8:54
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    $\begingroup$ My understanding is that rods are much more sensitive to light, which is why you don't see colors at dark. This also means that when there is enough light, rods are saturated, so there aren't really four different receptors in play under normal circumstances (unless you happen to have more than three different types of cones, which is not uncommon). That said, more than three components can be useful for other reasons, which is why printers use CMYK. $\endgroup$
    – Yuval Filmus
    Jan 21 at 8:56
  • $\begingroup$ This is interesting, I have never seen this graph before and I expected Rods absrobance to have a smoother curve than cones, but no. Anyway, to complete Yuval Filmus's comment, a lot of animals only have 2 different cones but birds generally have 4 with an additional one in near-infrared. Maybe future technologies will help us to experiment that... But can we say it adds image quality ? It depends what you mean by quality. Has a B&W image less quality that the colored one ? $\endgroup$
    – Optidad
    Jan 21 at 11:00
  • $\begingroup$ @YuvalFilmus Can we find a graph of cones and rods dynamic range somewhere? $\endgroup$
    – David Jonsson
    Jan 21 at 12:13
  • $\begingroup$ @DavidJonsson Certainly. I'm sure there is voluminous literature on the human visual system. $\endgroup$
    – Yuval Filmus
    Jan 21 at 12:14

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