Cadentis

Cadentis is a client-side mod for extended brightness configuration, heavily inspired by digitalshadowhawk's Gammabright mod. It allows you to control your in-game brightness from negative -150 up to 150 (vanilla Minecraft offfers 0 to 1).

To start using the mod, press the K key (configurable) to toggle on the mod. You'll see the following text on the top-right corner:

Then, use the Left and Right Arrows to reduce or increase your brightness in-game:

When you don't want to use the mod, toggle it off by pressing K again.