Colour vision

Unfortunately, we do not all see the same colours because the responses of individuals' retinal cones like all human characteristics vary quite considerably. Colour science has defined the retinal responses of what is called the 'Standard Obsever', an essential requirement before any comparisons or definitions of colour can be made in terms of human responces. The Standard Observer is an average of several 'normal' observers. In this sense, the word normal means having roughly the same retinal sensitivities. 8% of males have very serious deficiencies in sensitivity and are colour blind. Less than half percent of females deviate this seriously from the average. However, there are many people who are trichromates, that is who have the three types of retinal receptors but who are a little more deficient than average in some respect. They are known as anomalous trichromats.

Because all the problems of abnormal colour vision, even the normal amongst us have very variable vision. Both the lens of the eye and the macular area of the retina have a yellow pigmentation to protect the eye from excessive ultra violet light. With age, this pigmentation increases so that the perception of blue decreases with age. All these anomalies must be considered when the subjective assessment of colour is made. Though the eye is an excellent colour comparitor opinions may differ widely betweeb a supplier and his customer. They may not even be talking about the same thing. This is one reason for the ever increasing use of impartial colour instrumentation in industry.