I'm currently working on my first project containing composited elements. The plate is of course live action, it's a simple shot of a large open field. I am compositing a large water tower into the field.
I shot this project on 35mm film. I shot the tower separately and was planning on taking a single frame of the tower and removing the labels on it in photoshop. Then I was going to bring it into after effects and composite it into the field. Obviously I need to add grain so that it doesn't have the appearance of a still image.
My question is if the still image of the tower already contains grain, since it was was captured on film, how can I add grain? Certainly this will make the still image look real and live action, but will it then be twice as grainy? How do I go about adding moving grain on top of the still image which already is grainy by nature?