What are cone and rod cells

Why do both cone and rod cells need to be in the eye?

First of all - both the rod and the cone system measure the light intensity . Both sensory cells intensify their reactions when they are stimulated by more photons (Purves et al ., 2001). So your introductory sentence that rods recognize luminescence and cone color is wrong. They are both sensitive to luminescence.

You are right that rods recognize shades of gray while cones do color coding. Both systems can recognize gray levels. While rods are limited to this, tenons are not. Rods are very sensitive to light and can detect a single photon in a darkly adapted state. Therefore, they work at night in poor light conditions and as such convey night vision (scotope). Cones are photon-hungry and require more light to operate (photopic conditions).

  • Why do you have cones? Because color vision helps to see and differentiate between things.
  • Why rods? Because night vision helps.
  • Why both? Be well equipped to be successful in both light and dark environments.
  • Do we need both? No - even nocturnal hunters without rods have been shown to have been able to hunt at night. In addition, it has been shown that these geckos can see colors in starlight (Röll, 2000). Under these Lighting conditions rely on human Retinas on the pole system and cannot see any color.

-Purves et al ., Neuroscience , 2nd ed.Sunderland (MA): Sinauer Associates
-Röll, J. Neurocytol (2000), 29 (7): 471-84


But at night we wouldn't have been able to use only grayscale view with the help of cone cells to view images. The cones don't work at night?

AliceD ♦

Our cones don't work at night.


Since cones don't work at night, we need rods to help us with grayscale images.


@ Reptile1234 It's more that you need poles so you can see at night. The absence of functional rods leads to night blindness. As you can imagine, being unable to see at night affects survivability.