whats your frame like (CUs or wider)?
Im not sure about the lighting of the backround ....seems to me studios usualy of cyc lights which are usually just floods pointed at the backdrop to give an even exposure....atleast thats been my experience the one time i did something like that. if you use the space lights youll probably want to have flags on the backside to cut that light off your talent.
for the talent I think your fine this is pretty basic stuff. with a 5k you through diff you should have enough light for 4 at iso 400 I think.....you should check out the arri photometric calculator and you can put in your distance of the light to talent and it will tell you the stop your at....youll just need to calculate for light loss from the diffusion you are adding.
if its possible I would use a 10K and I would book light the talent from a bit more sidy of angle and maybe use a 12x instead of an 8x but that might be a budget thing for you? If you do a book light you can get away with prob 1/4 grid....at the very least Id put a 4x4 frame of light diffusion before the 8x frame also in that case you can prob get away with half grid. Double diffusion or booklighting always seems to give a more pleasing light to me then going through on layer of heavy diff
depending on how wide your shots are your fill might need to be larger as well and that will also probably want to come at a more sidey angle to fill the side of their face not getting hit by your 5k.
don't know much about the BMPC and IR though.
Edited by Albion Hockney, 21 December 2014 - 02:03 PM.