Can anyone explain why there is an * next to the wsRGB profile and why anyone would want to use that as their working space? Also questions about "HDR" floating point bitmap representation.

[Print Monkey]

So I've figured out that wsRGB is the "canonical" color space for the intermedite Windows Color System color space. Apparently it converts both SDR and HDR bitmaps into wsRGB before converting them to a monitor (device) output profile for the HDR (or SDR) monitor in use.

But can anyone explain:

1. Why would anyone want to use this as a working space since it seems like it's supposed to be some WCS internal thing?

2. Why do the applications allow you to select this with RGB8 when that's a very bad idea?

3. Isn't wsRGB supposed to be 16 bit floating point? Does Affinity Photo etc support floating point bitmaps?

[NotMyFault]

Unfortunately Affinity shows a list of all Profiles (installed on OS) and shows them to the user, including lots of profiles which won’t make any sense as document profiles, like printer or display profiles and those you reference. Nobody should use them except in rare (almost impossible) cases.

I made a feature request long time ago to filter them out to avoid users getting into trouble.

 

[Print Monkey]

Yes, I mean it seems like color management is usually poorly enough understood that there really ought to be a "show all profiles" checkbox that is off by default that will hide nonsensical profiles when it is off. I mean its good that you can select anything, but sometimes you don't want to see your four monitor profiles and your 20 photo printer/paper profiles appear as working space choices. And similar for print proofing view, hide anything that doesn't look like an output device profile unless a "show all" is checked.

In case anyone is using windows (especially windows 10+ with an HDR or wide gamut monitor) and wants to read up on the new super high tech "Advanced Color" WCS stuff in windows, it took me forever to find this because MS doesn't seem so great at organizing documentation but here it is:

https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range

Quote

The BT.2100 ST.2084 color space is an efficient standard for encoding HDR colors, but it's not well suited for many rendering and composition (blending) operations. We also want to future proof the OS to support technologies and color spaces well beyond BT.2100, which covers less than 2/3 of human-visible colors. Finally, where possible we want to minimize GPU resource consumption in order to improve power and performance.

When in HDR mode, the Desktop Window Manager (DWM) uses a canonical composition color space (CCCS) defined as:

• scRGB color space (BT.709/sRGB primaries with linear gamma)
• IEEE half precision (FP16 bit depth)

That provides a good balance between all of the above goals. CCCS allows color values outside of the [0, 1] numeric range; given the range of valid FP16 values, it can represent orders of magnitude more colors than the natural human visual range, including luminance values over 5 million nits. FP16 has excellent precision for linear gamma blend operations, but costs half the GPU memory consumption and bandwidth of traditional single precision (FP32) with no perceivable quality loss.

Automatic system color management

Windows is a multitasking environment where the user can run any number of SDR and HDR apps at the same time with overlapping windows. Therefore, it's crucial that all types of content look correct and at maximum quality when output to a display; for example, an sRGB (SDR) productivity app with a BT.2100 ST.2084 (HDR) video window playing over it.

When in HDR mode, Windows performs color management operations in two stages:

1. The DWM converts each app from its native color space to CCCS before blending.
2. The display kernel converts the OS framebuffer from CCCS to the wire format color space (BT.2100 ST.2084).
   • Optionally, the display kernel works with the display driver to perform additional display color calibration; for more info, see Windows hardware display color calibration pipeline.

 

 

My new laptop has a HDR display, but for some dumb reason HDR wasn't enabled in Windows by default even though the monitor profiles exist for it. And this "X-Rite Color Assistant" thing (which I think only exists to download some monitor calibration profiles created at the factory) refuses to work with HDR mode turned on for some reason. Sigh.

Anyway, I'm now wondering if the latest version of Affinity apps has been updated to use the windows "Advanced Color" since I'm trying to use that. See here for more info https://devblogs.microsoft.com/directx/auto-color-management/