i have watched many tutorials on how to reduce noise in cycles. however, no matter what i do its still grossly overflowing with fireflies. i must be missing something basic but i dont know what it is. i was watching a tutorial where he put the emitter plane in a hallway and changed its location and size and it made it crystal clear. i tried this and it just makes it worse. i have no idea what i am doing wrong.
Here is the tutorial i was watching.i was just trying to recreate the first example. https://www.youtube.com/watch?v=81k22ijYiIw

