Im not that experienced so maybe this is a really dumb question, but Im confused about exposure in low light situations.
Let me try and explain this easy.
Im usually navigating my exposure with False color on Alexa. And I was shooting a night scene where the actor is drawing on a "light-table" and the rest of the room is dark. Because it is night and she is drawing in a dark room. Nothing strange about that. (you can see on the first attached picture) I wanted most of the room to be dark and black in the end, after post. So I lit it like that. I watched false color and the parts that I wanted dark was purple and blue on false color. Fine I thought. But its noisy and grain in those parts. And im not really sure how to avoid this.
Should I have lit the whole room so the parts that I knew I wanted black wasnt black at the time of the shooting? And then make them black in post? Would that get rid of that noise because of the time of the filming it was information. If someone could explain to me the relations between on set exposure and after post, that would be awesome. But maybe its not that easy and im just to inexperienced.
I wonder for my self when I watch "real" movies and night scenes where there are parts in the frame that is completely black and is totally clean and no noise. Did they film it like that when they exposed? Were those parts "purple on false color" when they shot it. Or was it 20% and they fixed it In post. (picture 2)
If I know I want something black in the end product should I film it that way with no information on the sensor or should I light it and in post make it darker.
I hope you understand what im looking and sorry for not using the right technical words.