It is common to say that the YUV color model is inspired from the human visual system (HVS), knowing that we have many more rods than cones, and consequently, we are more sensitive to light than color. However, it does not seem to be that simple. Rods become active under low light conditions, and cones are not totally insensitive to light. These details seem to be ignored by the literature. My question is: is it reasonable to build HVS models for image processing only based on the number of rods and cones?
For instance, in the paper "A new color image quality measure based on YUV transformation and PSNR for human vision system" by Yalman and Ertürk (http://journals.tubitak.gov.tr/elektrik/issues/elk-13-21-2/elk-21-2-20-1111-11.pdf), a new quality metric called CQM is proposed. It consists in computing separated PSNRs on the Y, U and V channels, and combining them with a weighted average, whose weights are adjusted according to the number of rods and cones. But, once again, is it reasonable knowing that rods become active under low light conditions?