Computational Colour Science Using MATLAB, 2nd Edition

Chapter 9

Display Characterisation

9.1 Introduction

In this chapter we describe some methods for the characterisation of computer-display devices or monitors. The characterisation process for a CRT display is described in detail and a case study is presented to explain the step-by-step approach. However, it is noted that CRT displays have been almost entirely replaced in the consumer computer and television markets, being replaced by newer technologies such as LCD and plasma. CRT displays are still frequently used in research laboratories, however, where high colour fidelity is required and where the research teams may have substantial experience of characterising CRT display devices. LCD displays are increasing in popularity even in research environments and the chapter concludes with a discussion about the characterisation of these devices.

9.2 Gamma

The luminance generated by a computer monitor is generally not a linear function of the applied signal. Most CRT (cathode ray tube) devices exhibit a power-law response to voltage so that the luminance produced at the face of the display is approximately proportional to the applied voltage raised to a power in the range 2.35–2.55 (Poynton, 2002). The value of the exponent of this power function is sometimes called the gamma of the CRT or monitor. In a typical 8-bit digital-to-analogue converter, the lowest voltage will be coded by the value 0 whereas the highest voltage will be coded by the value 255  (2⁸ − 1).

The relationship between ...