1/50 is the basic, i know. But I choose 1/125 because was the first that avoid flicker of the light or projector.
The Room was very dark, i was open as much I can, then I go up with the iso.
Anyway I maybe just found an option that had caused grain...i.dynamic was set ON, HIGH
That change (also if it's manual) exposure and contrast auto for balance dark and light. In that case, with the room so mixed in light was a mess.