I think what really separates professionals from amateurs is presence of mind. Any of us can learn how to adjust to changing conditions on the fly, but a real professional remembers to DO it.
With all the gear I brought to the Grange last night, I left behind a moderately important tool: my brain. When the shooting situations changed, I did not change with them, and the images suffered.
Specifically, I erred in my assumption that the director wanted headshots. Instead, she wanted a couple of group shots, a couple of posed action shots, a whole cast shot (and the cast was much larger than I though it would be), and then, of course, the one thing I did expect: action shots of the actual rehearsal.
For the group shots and the posed action shots, I should have brought in my lighting gear and taken the time to light and compose them as photographs. Instead, I stuck with the on-camera flash and treated them like snapshots, which is what they look like. Worse, for the cast shot, I was so concerned about the on-camera flash overcooking the middle of the frame, I shot at too wide an aperture (to accommodate the ambient light), and lost the depth of field (apparent sharpness front to back) I really needed for three rows of people. To a very casual observer, I got away with it, but you and I know better.
Back in more familiar territory, I was able to capture some decent performance shots, including better images of one of the action poses we tried before rehearsal.
Another brain-fade occurred about halfway through the rehearsal. I’d been shooting in RAW, but seeing that my card was filling up, I switched to jpeg-fine. I did this, despite the fact that I had three more cards available. Following action across an unevenly lit stage, shooting in RAW might have helped me save under- and overexposed portions of images from the latter part of the show.
I got the bare minimum – a few publicity stills and a cast picture keepsake, but a bit more presence of mind would have helped me create better photographs.