Inconsistent display of images with color depth of 16 bits per channel

[flavonol]

Hi all,

I have a display that supports 10 bits per channel (bpc) color. When viewing images with a color depth of 16 bpc, Krita either displays the expected result (gradients have minimal color banding) or shows noticeable color banding that is no better than an 8 bpc version of the same image. The result seems to vary depending on the image & color space used. This inconsistency does not appear in GNOME Image Viewer (aka Loupe).

Any insights or troubleshooting suggestions would be appreciated. Thanks!

Images tested:

• jursonovicst’s gradient displays correctly, with less noticeable color banding in the 10-bit gradients. Color space used: “High Dynamic Range UHDTV Wide Color Gamut Display (Rec. 2020) - SMPTE ST 2084 PQ EOTF”. I’m not sure I notice a difference between the 8- & 10- bit gradients when I load the image instead using the sRGB profile.
• The 16 bpc version of my Blender sphere render shows pronounced color banding when loaded with the above Rec. 2020 color space, sRGB or “sRGB-elle-V2-srgbtrc.icc (Default)”.
• The 8 bpc version of that same render looks arguably better than the 16 bpc version.

System Specifications

Operating System: Fedora Linux 40 (Workstation Edition)
GNOME Version: 46 (tested with both Wayland & X11)
Krita package version: 5.2.2-7.fc40
Monitor: Acer ET322QK wmiipx (connected via DisplayPort)
Graphics card: Radeon RX 5700 XT

[Takiro]

Perhaps this thread is worth reading

10bit display output?

Question about 10bit display output in sRGB: My system is capable of using 10bit display output. That means: Instead of sending 256 shades per channel to the monitor it can send 1024 shades. The monitor is able to display those shades. If I create a 16bit rgb image in Krita (meaning 16bit per channel) it has 65536 shades per color channel. With this it can for example encode a very smooth gradient. When sending this gradient to a 10bit monitor it can not show all 65536 shades per channel but…

[flavonol]

Thank you for the link. It’s an interesting thread, but I’m unsure how to apply the information there to the issue I’m experiencing for two reasons:

1. As far as I can tell, color banding did not seem to be an issue for anyone in that thread.
2. They discuss Windows drivers, but I’m using Linux.

Edit: I suppose this could explain the banding I saw in the first gradient test with the sRGB color space, but the sphere render is still a mystery.

[Takiro]

As far as I know Krita doesn’t support 10 bit (or HDR) output on Linux especially because Linux itself does not support it. At least not x11, I don’t know about Wayland (I hard Valve is currently working on patches to make it work for their Steam Deck) but Krita is not ported to Wayland yet.