Limitations of visual gamma corrections in LCD displays

• Published in: Displays 2014-12, Vol.35 (5), p.227-239
• Main Authors: Alejandro Parraga, C., Roca-Vila, Jordi, Karatzas, Dimosthenis, Wuerger, Sophie M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Display; Display calibration; Electronics; Exact sciences and technology; Luminance matching; Observer-based calibration; Perceptual; Psychophysics; Visual gamma correction
• ISSN: 0141-9382; 1872-7387
• DOI: 10.1016/j.displa.2014.07.001

•We study a popular method for estimating the gamma of LCD displays.•Photometric measures of the angular dependency for different LCD technologies.•Psychophysical measures to support the photometric results.•We issue a series of recommendations to make the method more robust. A method for estimating the non-linear gamma transfer function of liquid–crystal displays (LCDs) without the need of a photometric measurement device was described by Xiao et al. (2011) [1]. It relies on observer’s judgments of visual luminance by presenting eight half-tone patterns with luminances from 1/9 to 8/9 of the maximum value of each colour channel. These half-tone patterns were distributed over the screen both over the vertical and horizontal viewing axes. We conducted a series of photometric and psychophysical measurements (consisting in the simultaneous presentation of half-tone patterns in each trial) to evaluate whether the angular dependency of the light generated by three different LCD technologies would bias the results of these gamma transfer function estimations. Our results show that there are significant differences between the gamma transfer functions measured and produced by observers at different viewing angles. We suggest appropriate modifications to the Xiao et al. paradigm to counterbalance these artefacts which also have the advantage of shortening the amount of time spent in collecting the psychophysical measurements.