On that subject, anyone know why shifting to HDR dims everything that way? My mental model of it is that SDR brightness goes from 0 to 100, and HDR brightness goes from -100 to 100, and that turning on HDR moves everything not HDR-aware down to the bottom of the brightness space.
I could look this up, but never think about it outside of conversations like this and figure it might be more fun to talk about it.
Well, it's pretty arbitrary. What is missing from most image (or sound) data is metadata to say what physical intensity is represented by the signal. I.e. how many nits (or decibels) should be emitted for this signal.
AFAIK, most encoding standards only define a relative interpretation of the values within one data set. And even if standards did have a way to pin absolute physical ranges, many applications and content producers would likely ignore this and do their own normalization anyway, based on preconceptions about typical consumers or consumer equipment.
To have a "correct" mixing, you would need all content to be labeled with its intended normalization, so that you can apply the right gain to place each source into the output. And of course there might be a need for user policy to adjust the mix. I think an HDR compositor ought to have gain adjustments per stream, just like the audio mixer layer.
In single mode where it’s just SDR, it’s mapped to take the full range of the display up to whatever is deemed a comfortable cap.
In a mixed HDR/SDR mode, the H is range above the S , so it doesn’t make sense to scale it up. I prefer Apple’s terminology of Extended Dynamic Range because it’s clearer that its range above the SDR range.
Now you could say that you intend for that SDR to be treated as HDR, but without extra information you don’t know what the scaling should be. Doing a naive linear scale will always look wrong.
Because windows map sdr contents to srgb color space. Which nobody except designers uses. Most monitor today ship with a much brighter and, high contrast, vivid color profile by default. If you toggle your monitor to srgb color profile. You should see a color that looks really similar to sdr contents in Windows hdr mode.
In my opinion, I also don't like it. But there is surely no way for Microsoft to chose a color profile that looks like without toggle hdr on given there are so many monitor manufacturers in the market. I think chose the most safe srgb option is understandable.
I have monitor that have 187% sRGB, 129% Adobe RGB and 133% DCI P3 gammut volume. But to have correct sRGB colors with maximum coverage on monitor I need to clamp ICC profile via Novideo SRGB. Without it, sRGB content looks oversaturated in orange spectrum.
It's more like SDR goes from 0 to 255 and HDR goes from 0 to 1024. In SDR mode, 255 = (say) 500 nits while in HDR mode 1024 = 1000 nits and thus 255 = 250 nits so SDR content looks dimmer.
SDR goes from 1-100. HDR goes from 0.01 to 100. Twice as many orders of magnitude difference from bottom to top. So if you peg the top to max brightness in both cases, the HDR looks brighter because the contrast is bigger.
(Note that this is an analogy. In other words, it's wrong, but a way of looking at it)
I could look this up, but never think about it outside of conversations like this and figure it might be more fun to talk about it.