Cones serve photopic or daylight vision and give rise to color sensations in addition to black, white and various shades of gray. The spectral sensitivities of rods and cones differ. Their spectral sensitivity is shown by the curve on the left, just above. Their spectral sensitivity is shown by the curve on the right. Rods and cones contain visual pigments that absorb light.
Cones come in three types according to the pigment that they contain.
Their spectral sensitivity function is shown on the right in the figure just above. The function on the left shows the spectral sensitivity of B-cones. Color vision depends on our having cones with different spectral sensitivities. Retinal sensitivity changes to increase absolute sensitivity during dark adaptation so that progressively less intense lights are visible. Full dark adaptation can take 20-30 minutes.