Sometimes when logging in and out of single player worlds and messing with your brightness you will go into a game and your game will be full bright. I do not know exactly what causes this but it happens. I do not believe it is my computers fault it seems to come from the game itself. It is inconvenient because you do not know where to place torches for when the glitch does not happen. It is able to be turned off by sliding your brightness down and then back up.