关于亮度以及校准你的显示器

Many are confused about brightness levels in content creation and consumption for SDR and HDR. Even content creators can get it wrong.
Blame for knowledge gaps not on people but on confusing standards. Finding needed info is difficult and free, well-organized info is scarce.
How brightness works with sRGB:
- sRGB is the most used colorspace today. Its draft specification is available.
- Defines reference display conditions (80cd/m², D65 whitepoint, transfer function) and viewing environment.
- Many wrongly assume to calibrate display to 80cd/m². But end users set display brightness based on environment. When creating sRGB content, take viewing environment into account.
- sRGB has a confusing transfer function with a linear bit for dark areas. Windows uses the wrong transfer function for sRGB content in HDR mode, making dark areas brighter.
How brightness works with HDR:
- Most HDR content uses SMPTE ST 2084 transfer function (PQ). It compresses luminance levels to match human eye sensitivity.
- Rec.2100 and BT.2408 define missing parts. Rec.2100 uses BT.2020 primaries with PQ transfer function and a recommended viewing environment.
- When displaying HDR content, take viewing environment into account and adjust luminance levels.
How this is handled in Wayland:
- Color management protocol in Wayland has reference display conditions and viewing environment attached to each transfer function.
- KDE Plasma's brightness slider configures reference luminance for content. Maximum reference luminance can be set in Plasma 6.3 display settings.
HDR in Windows games:
- Windows in HDR mode does sRGB wrong. With desktop monitors, there's an "SDR content brightness" slider. With laptop displays, it's a normal brightness slider.
- Most Windows games expect static luminance levels and ignore system settings. Linux native apps had workarounds that broke some features. In Plasma 6.3, workarounds were dropped and games need to adjust configuration.
How to implement good HDR:
- Use Wayland color management protocol.
- Get compositor and graphics driver capabilities.
- Get preferred image description and luminances.
- Adjust application when preferred image description changes.
- Render for parameters and set image description.
- Use reference luminance for SDR things.
- Check maximum mastering luminance to differentiate between "SDR" and "HDR" displays.
- Drop HDR settings from application.