If the type of dish you are using is the type that reflects light into a spreader first, then back out through the dish, then what I think it would do is (1) simply reduce the light or (2) perhaps if the dish were close enough, the light would bleed off faster. You would have a more dramatic contrast. The best way to see it is to shoot a solid backdrop from varying distances. In any event, what you're contemplating is very exotic light differences. In other words, chances are it's so minimal that you won't really notice any difference. I've seen all sorts of multiple light WOW factor set ups, and then you turn 90% of the lights off and get the same image, or nearly the same. In fact, Joe McNally explained in his most recent book *Minimalist Lighting* that once he had a gig with an art director. The art director didn't like the looks of Joe's two light set up and instructed him to use what she thought was appropriate for the job, which was around five lights. So he set it all up and shut all the lights off but the two he wanted. Art director loved it and said, "See, I told you we should use five lights." So there you go.
After reading many books on lighting portraits and other types of strobe lighting, Ive come to the conclusion that as a photographer I have to make several sometimes not simple choices: (1) Dramatic or happy, (2) Controlled light or area light, or somewhere inbetween, (3) which leads to the conclusion that you are only trying to use light and shadows to create the feeling you want. So you have a few soft boxes, a few umbrellas, lot of reflectors and translucent shoot through silks (nylon), a few grids, half a dozen stands, some booms, clamps, cine foil, gaffers tape and your good for 99% of it. The main thing is to understand it.
