Quote:
Originally Posted by Warner306
Soulnight's tool increases or decreases the target nits. Increasing the target nits raises the knee point further up the PQ curve to reduce compression, but it also changes the absolute brightness of all values relative to the output display.
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Actually what you are changing with the target peak nits parameter is the absolute (only relative to the mastering display luminances) value of the knee point, which affects all the values above it. After that, all the image values need to be normalized to the [0, 1] SDR relative range, which raises the global brightness. That's why I thought that the dynamic curves where doing the same, but after reading in more detail the specs this doesn't seem to be the case. For Dolby Vision the target luminances don't change, but for HDR10+ there is indeed a parameter called
TargetedSystemDisplayActualPeakLuminance which is a 2D LUT that affects all values, and is intented to take into account the "peak luminance that a display is capable of delivering while rendering the scene", which "depends on the spatial distribution of the luminance levels of the pixels in the scene and the power consumption limits of the display".