What is the purpose of color vision?

Human eyes can see in colour, thanks to 127 million light-sensitive cells on the back of the retina. These light detectors, called rods and cones, capture light rays from the lenses to create coloured images.

Rods and cones

About 120 million rods are sensitive to low light. They see in black and white and provide only minimal detail. About 7 million cones see colour and detail, but only in bright light.

Rod cells

The rods work well in dim light. They provide information about the whole image in shades of grey.

Cone cells

The cones detect colour and detail at the centre of the image, but only work in bright light.

Final image

Information from the rods and cones is gathered and transmitted via the optic nerve to the brain. This creates a full-colour image with fine detail.

Three colours

There are three types of colour-detecting cones inside the eyes. They are sensitive to red, blue, or green. But combined, they can detect millions of colours, all made of mixtures of these three basic colours.

Blue, green and red are known as the primary colours. Secondary colours are where two primary colours mix. White is a mix of all three primary colours. Yellow is a mix of red and green.

 

Picture Credit : Google