Diagnosis and genetics of defective colour vision / by H. Kalmus.

  • Kalmus, H. (Hans), 1906-1988.
Date:
[1965]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Diagnosis and genetics of defective colour vision / by H. Kalmus. Source: Wellcome Collection.

    17/134 (page 1)
    CHAPTER II ESSENTIALS OF COLOUR THEORY The literature of colour theory is enormous and very confusing. For the purposes of this book, however, it is sufficient to clarify those points which are essential for the recognition and classification of defective colour vision. To the naïve mind colour is an attribute of objects: violet is the colour of violets, orange that of oranges. In many languages the same words are used for colour and for paint. More sophisticated is the view that any particular colour is an attribute of a particular species of light characterized by its degree of refrangibility (Newton, 1672) or as we say today by its wavelength. Indeed visible radiation of a particular wavelength (monochromatic light) has in certain well- defined circumstances a characteristic colour for the normal observer. But the colour of some (e.g. brown) objects cannot be matched by spectral Hght of a particular wavelength while most naturally occurring colours (hues) whether red, yellow, green or blue may be produced by an infiinity of mixtures of monochromatic radiations. The additive laws governing those mixtures we shall show (p. 4) to be funda¬ mental for the understanding of normal and of defective colour vision. On the other hand, a colour sensation mediated by the impact of monochromatic radiation on the retina is greatly dependent on the radiation intensity (Purkinje, 1823-25), the size and locahzation of the affected retinal area (Maxwell, 1870), the illumination of neighbouring retinal areas (simultaneous contrast, Hering, 1878), and on previous conditions (successive contrast). We must thus conclude that there is no unique, and not even a simple, relation between wavelength and colour sensation. In spite of these complexities it is not too difficult by using certain constraints and by standardizing the conditions of testing to establish individual differences of colour perception and to explore many aspects of this variability. Normal observers can match the colour of any hght—whether seen through an instrument or reflected from a surface—by miying 3