Diffuse White Level of Most Episodic HDR Content Nowhere Near 203 Nits

We’ve written elsewhere that the majority of HDR narrative work has a diffuse white level much lower than that recommended by the ITU and that it’s a constantly shifting target. This may frustrate those desperate for hard and fast rules, but this approach has a number of advantages, not the least of which is that it accords the colorist considerable artistic freedom to set aside that additional reserve for individual scenes to powerful dramatic effect. Another benefit is that a lower diffuse white level leaves additional headroom for more impactful specular highlights. LG Electronics’ EP950 UltraFine OLED Pro Monitor Best Practices and Additional Usage Information confirms that most theatrical and episodic content takes a much more conservative approach toward diffuse white:

“The ITU-R BT.2408 document describes a reference (i.e. diffuse) white level for HDR content of 203 nits. It might seem logical therefore to render SDR content at 203 nits peak, by simply scaling the luminance. Recent research suggests that this approach does not preserve the ‘look’ and ‘creative intent’ of SDR content. In addition, despite ITU recommendations, most theatrical and episodic HDR content does not have a diffuse white level of 203 nits. The diffuse white level in such content usually changes from scene to scene, and is far closer to the typical diffuse white level of SDR content of between 80 and 100 nits at most. LG therefore suggests setting the SDR peak luminance at SDR standards based levels using a value of < 4 on the ‘HDR/SDR brightness balance’ slider.”