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Re: HDR question

Re: HDR question

Nick Shaw

On 17 Mar 2018, at 16:06, alister@... wrote:

I really hope they aren’t different. What would be the point of my expensive DSC Charts?

Sure, it can be different, but it doesn’t have to be, it all depends on the grade. If the camera and monitor gammas are properly matched then capture and display range should also be matched. The engineers didn’t spend decades developing different gammas to make the pictures on monitors look different to the scenes we are shooting. They were developed to make them look the same

That's the key point, "look the same" not "be the same." It has long been accepted in traditional TV that a system gamma of about 1.2 was required to make an image on a TV appear perceptually the same as the scene.

Intuitively you could think that with HDR it might be possible to have the absolute luminance of the screen be identical to that of the scene, and therefore require no system gamma or other picture rendering. However, while this might be possible for some low contrast scenes, where there are specular reflections of the sun, or even just a bright sky, in the scene, co current monitor can reproduce that.

Look up the BBC's experiments when developing HLG (Google Tim Borer and Andrew Cotton). They found (surprisingly, according to classical colour science) that as the peak brightness of the monitor increased, the system gamma had to be increased to get a perceptual match. For a 1000 Nit monitor in a typical environment, HLG uses a system gamma of 1.4.

Nick Shaw
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