Blocklight appears to have become darker at full brightness settings between 1.21.8 and 1.21.9. This is particularly visible with light sources and shadows, which have become noticably darker.
Steps to reproduce
Open the game in 1.21.8
Set brightness to “Bright”
Enter a lit indoor space
Reopen the game in 1.21.9
Observe that the space now appears darker
Hi!
Thank you for your report!
We're already resolved this issue at MC-301822, so I will resolve and link this ticket as a Duplicate.
I suggest also to browse through the main issue for potential fixes.
Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki