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Re: HDR question

Re: HDR question

Nick Shaw

On 16 Mar 2018, at 13:19, alister@... wrote:

Nick, could you enlighten me as to how the contrast ratio of a display is different to the contrast ratio of a scene, surely a ratio is a ratio, if a screen can show 10:1 and a scene is 10:1 are these ratios not the same?

A scene and display contrast ratio of e.g. 10:1 may be numerically the same, but they are not perceptually the same, because there is a difference in both the absolute luminance and the viewing environment.

To make an image appear perceptually like the scene to a viewer, you do not want the luminance of the screen to be proportional to the luminance of the scene. You require what is referred to as "picture rendering" applied. This is the function of the RRT in the ACES block diagram, or the 1.2 "system gamma" of traditional video, to give two examples.

Nick Shaw
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