COLOUR VISION TESTINGReference has

COLOUR VISION TESTING

Reference has previously been made to the fact that a proportion of males, in particular, may have defective colour vision. It is important, therefore, that all people engaged in the reproduction of coloured illustration or in colour matching, should be carefully assessed for their ability to make correct colour judgments. This can only be done with the aid of some form of colour vision test.
the best known test, for determining defective colour vision, is probably the Ishihra. It consists of a series of printed plates on which the subject sees coloured spots out of which may appear a number, it is an indication of possible defective colour vision. The test has limitations and is really only capable of signaling that a subject is suspect and has one of the more obvious deficiencies. However, it is a valuable test method for screening out those who need more sophisticated examination.


Colour aptitude testing

Persons having normal or defective colour vision will vary in their ability to discriminate between colours having very small differences. This ability is obviously of major importance in ink matching, proof passing and press control. The test used by Pira to assess this is typical of most and is that of the Inter Society Colour Council (ISCC).
The test consists of an inclined board on which are mounted four rows of coloured plastic chips. The colours being yellow, green, pink and blue from bottom to top. The tester has a unit containing the other half of each of the coloured plastic chips which are dispensed in a random order. The subject is given one chip at a time and asked to select the best match. When a decision is made, the first chip is returned and the test proceeds with each of the 48 chips in turn.
The test should be carried out under standard lighting conditions. The person being tested has a maximum of one hour to complete the test, during which time he/she should be free from distractions, to ensure a standardized test method. All matches have near alternatives and are scored with 1, 2 or 3 points depending on the accuracy of the match. The scores are reported as a percentage score overall and for each subject colour. The average score for printers measured by Pira is around 65% and the best score to date is 90%. It should be noted that there is normally a falling-off in discrimination scores with age, due to the physiological ageing of the cornea and lens. This effect is most marked in yellow discrimination.