Boosted Brightness is a simple clientside mod that allows you to set your brightness beyond default levels to your liking. It makes use of Fabric (not Forge) and is compatible with 1.16.
New Brightness Slider
The mod modifies the brightness slider in video settings, extending brightness range to 1200%. I found 200% - 500% to be a fair compromise between being able to see the darkest areas clearly and actually seeing differences in lighting. 1200% is full-bright.
Max Brightness Toggle
A configurable toggle to swap between your set brightness and the maximum brightness.
The screenshots below compare various brightness settings in different situations. "Moody" is 0% and 100% is the usual "Bright".
Cave brightness comparison
Nighttime brightness comparison
(1) Install Fabric
(2) Drop the Fabric API jar into the mods folder
(3) Drop the Boosted Brightness jar into the mods folder
Works with Optifine. Let me know if you find any compatibility issues.
MIT. Feel free to use this mod in any modpack.