Requires the library mod Collective.
Full Brightness Toggle is a client-side mod which allows players to instantly turn the brightness (gamma) to full with the press of a button. By default it's G, but this can be changed in Options -> Controls. Created after reading a request from someone with impaired eyesight, who needed this feature to play the game. Don't use it on servers where it's not allowed. When in doubt, ask first.
The feature in action:
The keybind can be changed in the in-game options menu:
You may freely use this mod in any modpack, as long as the download remains hosted within the CurseForge ecosystem.
Serilum.com contains an overview and more information on all mods available.
Comments are disabled as I'm unable to keep track of all the separate pages on each mod.
For issues, ideas, suggestions or anything else there is the Github repo. Thanks!