Impaired colour vision

Colour vision deficiencies can vary greatly. We have three types of cone cells, any of which may perform less efficiently than the others. Additionally, our sensation of colour is affected by brain functions, leaving a lot of room for variation. In fact, perfect colour vision is more of an exception than the rule, and most people have some type of impediment in this respect. The most common deficiency known as “red-green blindness” is due to the abnormal operation of the cone cells sensitive to green – they are also sensitive to red. Colour blindness or impaired colour vision does not usually affect the life of the person involved. He or she may not even be aware of it unless tests have been made. All of us adjust to living with our own sense of sight and are used to it.

Visible colours - CIELab

A universal system has been adopted for defining colours with three numbers: the first one represents brightness, the second one colour on the red-green axis, and the third one colour on the blue-yellow axis. Lab colour definitions are specifically related to the perceptual capacity of the human eye. Colours defined with CIELab values should look the same anywhere in the world, irrespective of the technology used to produce them. All technical methods are nevertheless subject to limitations. For example, not all the colours that occur naturally and are perceived by the eye can be displayed on screen, even though the range of colours is fairly extensive. The percentage of the CIE colour range that is reproducible on screens or printing paper is shown in the image. The richest and most saturated colours are the hardest to reproduce.