I'm considering trying out flash photography for stage and musicals. Permission has been granted so that is not a problem. My main problem is that the subject to background seperation is not very great under the best of circumstance. Is there anyway i can generate enough output from my flash to sufficiently light up the subject while still maintain a black background? Any ideas on setting? Current setup is a 1d with 2 550ex and the usual 2.8 zooms.