Computational Colour Science Using MATLAB, 2nd Edition

Chapter 7

Physiological Colour Spaces

7.1 Introduction

The system of colorimetry based on the CIE (1931) standard observer is still widely used in industry as it provides a convenient specification of the colour of a stimulus. For example, it is possible to reproduce a colour with acceptable approximation if its CIE (1931) xy chromaticity coordinates are known. Although this colorimetric information is based on the colour-matching performance of the ideal observer, it does not provide any information about the colour appearance of a stimulus. This is because the stimulus coordinates are not a direct representation of the physiological mechanisms that allow us to see that colour. The CIE (1931) chromaticity coordinates (and all the other CIE colour spaces which are based on it) provide numbers which have no physiological meaning. Several laboratories have attempted to describe the relationship between the colour matching functions (CMFs) and the physiological responses of the human visual system, also known as the cone fundamentals. These attempts have revealed important inaccuracies of the CIE (1931) CMFs. For these reasons, the widely accepted cone fundamentals estimated by Smith and Pokorny (1975)¹ and Stockman and Sharpe (2000) are based on the Judd-Vos modified CIE (1931) CMFs and the Stiles and Burch (1959) 10° CMFs, respectively. Perhaps, it would make more sense if colorimetry was actually based on cone fundamentals rather that CMFs, a thought that was also put forward by ...