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which are the two types of receptors in the retina?
The retina is the array of light receptor cells that lines the back of the eye.  It  contains two types of receptor cells, named after their shape; rod and cone cells, and interconnecting ganglion cells, of which there are two types with differing properties, X and Y cells.

Receptor Cells

Rod Cells

120 million rod cells per eye.
Mainly at the periphery of the retina.
Sensitive to low light levels.
Do not resolve details.
May be saturated.
When active, they suppress cone receptors.

Cone Cells

6 million cone cells per eye.
Concentrated in the fovea (the pit in the retina at the centre of the visual field).
Less sensitive than rods.
May be saturated, which results in the complementary colour being seen in an after image.
Three types, each sensitive to light of different wavelengths — the colours red, green and blue.
Only 3-4% of receptors in the fovea are sensitive to blue light, so blue detail is more difficult to perceive.


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