An Improved Method of Visual Gamma Correction for Lcd Displays

In this study an improved method for visual gamma correction is developed. Eight half tone patterns were designed to generate relative luminances from 1/9 to 8/9 for each colour channel. A psychophysical experiment was conducted to find the digital count corresponding to each relative luminance by visually matching the half tone background to the uniform colour patch. Both interand intra-observer variability for the eight luminance matches in each channel were assessed and the luminance matches proved to be consistent across observers (∆E00<3.5) and repeatable (∆E00<2.2). Based on the individual observer judgements, the display opto-electronic transfer functions (OETF) were estimated by using 3 rd order polynomial regression. The performance of the proposed method is evaluated by predicting the CIE tristimulus values of a set of coloured patches using these observerbased OETFs and comparing them to the OETF obtained from actual luminance measurements. The resulting colour differences range from 2 to 4.6 ∆E00. We conclude that this observer-based method of visual gamma correction is useful to estimate the OETFs for LCD displays. Its major advantage is that no particular functional relationship between digital inputs and luminance outputs has to be assumed.