With which shader / mod does BastiGHG make its world so bright?

Do you know which shader BastiGHG uses to zoom or how it can make Minecraft brighter?

Optifine and Gamma?

Hi
That could be because Basti GHG uses the Badlion client. There's the fullbright function that makes everything bright

He zoomed in with Optifine

He probably turns Fullbright on and off with the Badlion client, but you can also simply set gamma to 10 in options.txt in the .minecraft folder