The effect of brightness on colour recognition under water

Abstract

Water distorts the colours of objects compared to the situation in air, and it is relevant to enquire how this affects divers' colour recognition. Twelve divers (eight in the laboratory and four in a field experiment) were required to determine the distances at which colours could be correctly identified in different types of water. Changing a target's brightness (keeping hue and saturation constant) significantly changed its recognition distance. In addition, reducing the reflectance of a target having a similar hue to that of the background reduced its recognition distance relatively more than targets with hues offset from that of the background. Consequently, classification by hue name alone was insufficient to allow an unambiguous rank ordering of the relative recognition distances of the different colours. In situ light measurements in the field study permitted the specification of the spectral characteristics of the targets and their visual background. Such data are important if a colour recognition model is to be established for situations involving gross spectral distortion.

Keywords:

• Colour vision
• Brightness perception
• Underwater effects

Additional information

Notes on contributors

PAUL G. EMMERSON

To whom requests for reprints should be sent. Current address: Department of Vision Sciences, Aston University, Gosta Green, Birmingham B4 7ET, England.