Colorist Asa Shoul, on more than one occasion, including during an interview with Variety, counsels cinematographers, “When discussing the dos and don’ts of HDR, I would advise not placing actors in front of windows as the extra brightness that can be seen in the sky might make the actor appear less visible.” Which is among the most oft-repeated misconceptions when it comes to shooting HDR, as it’s been pretty well established by now that not only do audiences not have any vexing issues with actors or any other of god’s creation in front of bright windows but that they actually prefer greater realism and dramatic lighting. The same could be said for practicals, which colorists devote untold hours of their professional lives trying to suppress. Ironically, in The Crown, there are innumerable shots of characters placed directly in front of windows; though regrettably, in nearly all instances – in the earlier seasons at least – the brightness of those windows is mercilessly knocked down toward middle gray, effectively destroying whatever impact the shots might have had. Regarding exploiting HDR’s extended range, during a webinar, Shoul disclosed that The Crown was graded to 100 nits, with a speed limit of around 400 or 500 nits reserved for highlights. In HDR, fully one half of the PQ EOTF is allocated to highlights; and it should be noted that, unlike in SDR, where highlights refers to things like a white table cloth or wedding dress, in HDR, it concerns specular highlights and emissive light sources. Most colorists are placing diffuse white somewhere between 140-240 nits or thereabouts. Due to the logarithmic nature of the human visual system’s (HVS) response to light, placing highlights at 250-300 nits fails to produce a sufficiently differentiated experience between scattered, diffuse white and a shaft of sunlight pouring through a window, a chandelier or a light bulb; which is why, for specular highlights and emissive sources, something in the neighborhood of 3X that of diffuse white is a rough rule of thumb. Concerning which, regardless of what one makes of Dolby’s studies of viewer preferences, it becomes clear that, irrespective of peak brightness, participants unfailingly preferred specular highlights to be several times brighter than diffuse white. Which could be why, although unable to precisely articulate the reason, John Daro, Lead Digital Intermediate colorist at Warner Post Production Creative Services, has remarked, “There is no set standard for what is considered HDR brightness. I consider anything over 600 nits HDR.” After all, if specular highlights are little brighter than diffuse white, we’re really no longer talking about HDR, but brighter SDR. Somewhat surprisingly, viewers have even been known to prefer clipped highlights to those that are of low luminance. As it happens, it appears that the colorist and cinematographer Adriano Goldman make bolder choices with regard to brightness in season 5 of The Crown.
The last eight words of this passage from an article published by Barco are key:
“This is closest we ever got to a specification for HDR in the movie and TV industry. SMPTE defines it without quantified metrics: “A High Dynamic Range System (HDR System) is specified and designed for capturing, processing, and reproducing a scene, conveying the full range of perceptible shadow and highlight detail, with sufficient precision and acceptable artifacts, including sufficient separation of diffuse white and specular highlights.”
Barco
Disclaimer: we most certainly did not watch all 50 episodes of The Crown, we only skimmed through some of them.
The Daejeon Chronicles 
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