I tend to do this; I put a reflector on the strobe (just to prevent direct lighting) and bounce the light off a nearby wall/ceiling intersection to give a ~3m diameter diffuse light source. I have a 1kJ flash, but often run it at about 350J (-1.5 stops) to get about f/8 in my pale-yellow living room. With a 400speed film, you will get f/16 no problem and the light looks very natural. If you don't have enough light, move a bit closer: the inverse-square law is powerful!
As a stopgap measure, I sometimes use a small (60cm) softbox with a battery powered flash (Minolta 5600 is unusually grunty; expect maybe 1 stop less from a Vivitar or whatever 50m-GN flash you have). That gets me f/16 at 1m, which means you should get f/16 at 2m with ISO400. A silvered umbrella should be even more efficient, especially one of the high-efficiency collimated/parabolic ones.
Last edited by polyglot; 12-10-2012 at 05:43 PM. Click to view previous post history.