National Physical Laboratory

The eye's response to colour

Red - Green - Blue dotsAnother interesting aspect of the human eye's function is that we are most sensitive to green light - that is to say that if we are presented with three separate lights coloured red, green, and blue of equal optical power we would perceive the green to be the brightest.

This phenomenon is demonstrated by the following graph, which shows that the human eye's visual response peaks in the region of the spectrum that corresponds to wavelengths of green light.

The spectral response of the human eyeThe spectral response of the human eye

Did you know?

Did you know? Incredibly, the eye's colour response to green light is so strong that if you looked at the spot on a wall produced by a 1 milliwatt green laser pointer as compared with some 1 milliwatt red laser pointers, the green laser pointer spot would look approximately 30 times brighter.

As you can see the blue and red regions at either end of the spectrum elicit the lowest visual response, i.e. they appear the least bright to our eyes.

Not all of us perceive colour in the same way. For example, 8% of the male population has a colour perception difference that is usually described as 'red-green colour blindness' due to the lack of the red or green retinal photoreceptor in their eyes.

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