Rendering Digital Cinema and Broadcast TV Content to Wide Gamut Display Media

Much more is possible in achieving brighter, more vibrant colors for a richer visual experience in emerging, wide-gamut display media. Yet, both digital cinema and broadcast TV content fall well short of this promise. In this paper, we provide the means for realizing this promise by identifying certain memory colors (e.g., green grass, red, and blue sky) and rendering each independently making use of the full gamut of the display media while identifying and maintaining flesh tones to their original intent. Further, a means is provided for extending the gamut of not just wide-gamut, but any display media by simply lowering the white point of the display. 1. Background and Objective In emerging display media technologies, e.g. wide-gamut, LED backlit displays, much more is possible in achieving brighter, more vibrant colors for a richer visual experience. Yet, both digital cinema and broadcast TV content are based in standards 1,2,3 whose gamut falls well short of this promise. And attempts to globally expand this content out to the brighter, more colorful primaries of wide-gamut displays have been met with the hue and cry of unnaturalness 4 . Have we been so conditioned to these standards most of us since childhood that we consider video and cinema as a separate reality from what we see every day? This paper asserts that perhaps not, that it is instead a matter of rendering. That certain features of a scene – specifically flesh tones and perhaps certain object or surface colors should be rendered as original while other features such as a blue sky on a crisp winter’s day, a sunset, or a colorful arrangement of flowers are clear candidates for brighter, more colorful renderings. 2. Methods and Results A number of tools 5,6,7,8 are available for rendering digital cinema and broadcast TV content to wide gamut display media under given conditions of intent. In this paper, that intent is to identify certain memory colors (e.g., green grass, red, and blue sky) and render each independently making use of the full gamut of the display media while identifying and maintaining flesh tones to their original intent and maintaining luminance. This is carried out by an application of sigmoidal-like transformations on the color attributes in a linear appearance space like CIELAB 9 and, as light and dark adaptation are modeled in such spaces, mediating the perceptual gamut of a display media as a function of its surround or viewing conditions. 2.1. The transformation in IPT space The appearance space CIELAB has reasonable perceptual uniformity in chroma, but is less than uniform in hue particularly in the reds and blues. Hence, the appearance space IPT 10 , a appearance space based in opponent color theory, was chosen as perceptually uniform in hue. Figure 1 illustrates plane of constant hue for a particular display in Luminance L, analogous to intensity I in IPT space, and chroma C as the geometric distance from neutral to a color value at constant intensity.