It’s also that I’m pinged all over the place since early December, I try to answer everyone quickly, but that often involves reading in diagonal between cooking supper, coding math and spending a bit of time with the wife, so I don’t overthink stuff before writing it. Plus, as many here, English is my third language so when I’m tired, it becomes French translated 1:1, which sounds a lot harsher than what English natives are used to since we don’t do euphemisms.
Bottom line, I apologize, I wasn’t targeting you personally. My point was that histogram, as any other scope, is meant to make your life easier, so if it doesn’t, just disregard it. As I said somewhere, scopes are useful to diagnose where issues come from, as long as the picture looks good, don’t bother.
The “darkest tones” are contextual. The PQ curve really dilates lowlights a lot. First, you don’t need to have true blacks (aka RGB = 0), then it’s all about axes scaling.
sRGB is a safe choice indeed. Black points don’t exist in reference spaces, since they are not tied to a medium, so it’s only a matter of encoding range. And, given that many printing drivers don’t do black point compensation, not having RGB = 0 can be a safety jacket.
And you know that because… ?
HDR formats usually encode RGB over 10 bits, that is 1024 code values. So 1023 encodes 1000 nits. But, for obvious compatibility reasons, all HDR formats encode 100 nits (aka standard SDR white) at 255, which is the max in 8 bits. darktable’s histogram shows the 0-255 range in 8 bits, no matter the color space. So, the 100% of the histogram is still SDR white, thank you very much.