How much impact will a off-camera sb600-sb910 have in a 500-700 sqft room if you already have a 800-860 wattsecond monolight?

I am considering a monolight in the range of 800-860

wattseconds for high speed sync to photograph 7-10 people in

a 500-700 square foot room because I assume that would be

powerful enough for 10-15 feet away from the subjects in that

large of a room. The question I have is how much would a

single small off-camera speedlight (like the sb600--sb910) have

in addition to that monolight in that setting in that sized room?

<p>The SB-910 speedlight mode at full power would compute to be 75 watt seconds. The SB-600 at least 60 watt seconds. The reflector choice makes all the difference (zoom for example), and watt seconds loses some meaning when you apply umbrellas or softboxes.</p>

<p>HSS mode would be about 20% of that level. Why would you need HSS for a group of people? Are they running? But indoors, the speedlight flash itself is faster than the HSS shutter speed.</p>

It depend on what you withboth. Use the monolight to create the overalllight and the Speedlite as a key light spot, as a fill

light or as an accent light and yes it will have an effect.

I'm not sure why you're specifying the room area.

The exposure for the group of people will depend

only on the flash power + modifier used and its

distance from them.

If you don't want a dark background, then that's a

different issue and will need additional lights or a

bounce technique. It also depends whether your

500 to 700 square foot room is 50/70ft by 10ft, or 22ft/26.5ft square. Plus the ceiling height is more significant when it comes to bouncing the flash.

It might help if you could tell us what effect you're after.

The additional light supplied by a little camera mounted speedlight to an 800 joule monolight will be negligible as far as exposure is concerned.