Testing colour confusability among a new range of decimal stamps

✍ Scribed by I.D. Brown; A.J. Hull

• Book ID: 102988911
• Publisher: Elsevier Science
• Year: 1971
• Tongue: English
• Weight: 622 KB
• Volume: 2
• Category: Article
• ISSN: 0003-6870
• DOI: 10.1016/0003-6870(71)90075-5

✦ Synopsis

Two experiments are reported in which the objective was to achieve minimal confusability among 14 colours required for the new lower-value range of decimal stamps. The ma in conclusion is that aesthetic considerations are largely incompatible with the criteria required to meet this objective. A symmetrically structured range of seven bright hues, each used at two levels of saturation, was found to have some advantages over an alternative unsymmetrical range which included more pleasing colours. This was mainly because the latter included greater variation along the brightness dimension, which produced large errors in recognition of darker hues. It could also have resulted from the greater nameability of colours made possible by combining hue and saturation cues systematically. The findings emphasise that absolute confusability of colour displays cannot be assessed reliably by viewing stimuli side-by-side, because this does not involve the imperfect mechanisms employed in colou r recognition.

Colour is probably the primary cue used to identify low-value postage stamps. This is particularly true for postal sorters and, to a lesser extent, for Post Office counter clerks, but it also holds, within limits, for the majority of the general public. When the lower-value range of decimal stamps had to be designed, it was therefore essential to ensure that the possibilities of colour confusion were minimal. Contributing to this requirement was the economic constraint which forced retention of the earlier stamps' format, in which printed value is neither readily legible, nor consistently positioned. The Post Office, for what is thought to be the f'trst time, took this opportunity to request human factors studies of confusability before accepting proposed designs for the new range.

Apart from being visually discriminable, colours of postage stamps have to meet a number of other criteria.

1. They must be aesthetically pleasing, mainly to meet philatelic demands. These can be of considerable economic importance.

2. They must be capable of reproduction within fine tolerances during the printing process.

3. They have to provide an identifiable signal from the phosphor strip which stamps carry for mechanical sorting.

Considerations of this kind produced a short-list of 25 fairly acceptable colours on which confusability data were required. The objective of Experiment 1 was to construct a confusion matrix from which the 25 stamps could be ranked for difficulty in identification. This rank order could then be used to select the 14 more discriminable colours which were initially needed for the new lower-value decimal range. The matrix could also be used to 'value' colours, so that the more commonly used stamps, eg those required for the first and second class mail, could be selected from extremely highly discriminable pairs.