Hitting the Mark—A New Color Difference Metric for HDR and WCG Imagery

Abstract

With the emerging demand for high dynamic range (HDR) and wide color gamut (WCG) technologies, display and projector manufacturers are racing to extend their color primaries in the cinema and in the home. With these brighter and wider colors, the question is: in calibration, how close is close enough? This answer is increasingly important for both the consumer and professional display/projector market as they balance design trade-offs. With HDR/WCG technology, an increasing issue is that many of the color difference metrics in common use today, such as $\Delta E_{00}$ , substantially deviate from human perception and become unreliable for measuring color differences. This causes under and over prediction of color differences and can lead to suboptimal design decisions and difficulties during calibration. There is a large amount of perceptual color difference data in the field today; however, the majority was collected using reflective surfaces and very little reaches the boundaries of modern display capabilities. To provide a better tool for facilitating design choices, this paper will present a ground truth visible color difference data set. These visual experiments were conducted between luminance levels of 0.1 and 1000 cd/m 2 on HDR laser cinema projectors with approximate BT.2100 color primaries. We present our findings, compare against current metrics, and propose specifying color tolerances using the $\Delta $ IC T C P metric for HDR and WCG imagery.