I am wondering if discharging 2 Nikon SB 200 flashes in close proximity and simultaneously would have an equivalent power to say a Nikon SB 600. I would only be using The SB 200 for close up work such as small group shots within 10 feet and possibly the odd portrait shot. These flashes would be used in conjunction with a SB 800. Any advice would be appreciated.
Sorry, but the SB-R200 is a tiny flash. It would take seven SB-R200 to match one SB-600 (if zoomed to its minimum 24mm). And FWIW, 16 of them to match the SB-600 zoomed to 85mm.
The Guide number of a SB-600 is GN 85 to 131 (24mm to 85mm zoom). (ISO 100, feet)
The guide number of the SB-R200 is 33 (feet, ISO 100, no zoom).
The guide number of multiple identical flashes is square root (number of flashes) x GN 33 (of each)
If the number is 2 flashes, then 1.414 x 33 = GN 47 (ISO 100)
If the number is 7 flashes, then 2.6 x 33 = GN 87 (ISO 100)
Guide number is distance x aperture (all same units, like feet).
The meaning of GN 47 is that at ten feet, you could use f/4.7 (ballpark, full power, ISO 100).
ISO 200 multiples GN by 1.414, so GN 47 becomes GN 66 (f/6.6 at 10 feet, ISO 200)
This may be enough for fill, if you used the SB-800 for the main light. Fill can be one stop down (half power).
WayneF is right, they are in no way powerful enough for group shots.
I have made a "ringflash" rig consisting of 6x SB-R200's and even then it's not enough power to shoot full length portraits a narrower apertures.
But for portraits the rig works incredibly well, mounted on a 50mm on my D700 I can shoot portraits at any shutter speed and almost any aperture.
