Mesopic vision (twilight vision): Definition
Mesopic vision is the transitional state from seeing by day (photopic vision) using the cones, to seeing by night (scotopic vision) using the rods. This is why it is also called twilight vision. Upon decreasing brightness, our colour perception and visual acuity deteriorate until we finally only recognise differences in brightness.
Good to know:
Experts speak of mesopic vision between luminances of 3 cd/m2 and 0.01 cd/m².
