So yesterday was "studio shoot" day for some of my photography students (and some from another class). Needless to say, it was a massive amount of work. But it was still fun and educational.
Since we had to work with a lot of students we split things up and had them shooting in groups of 3 or 4 at a time. We standardized the lighting setup with a couple of Alien Bees with umbrellas (the school doesn't have any soft boxes). I had every student set his/her camera to manual exposure, ISO 100, 1/125 shutter speed and f/8. And since the school only has one radio trigger we had everyone use their camera's pop-up flash to optically trigger the main strobes. This setup worked well. Except when it didn't. Some cameras just didn't get along with this and produced dark photos. In fact, some (not all) produced uniformly dark shots even after changing aperture. I'd have two students with budget Nikons set to identical configurations and one would work perfectly and the other wouldn't. (Unfortunately, due to the number of students coming through, I didn't have time to make a list of cameras that exhibited the problem and those that didn't.) After she shoot was all done I think I worked out what was going on: I believe it was caused by the pre-flash that DSLRs use to meter before the main flash. I don't know the details but I suspect the pre-flash was triggering the studio strobes before the shutter had a chance to open. Of course, when you're on manual exposure there's no reason for the camera to have a pre-flash at all, but it may be left on because the manufacturer didn't want to add additional code to the firmware (in the case of the cheapest cameras). The cameras that seemed to yield a uniformly dark exposure regardless of aperture may have been operating in manual mode as far as ambient light was concerned but modulating flash power independently. Anyway, we solved the problem by letting any student whose camera had trouble shoot for a while with the radio trigger. Whew. A lot of work. But very gratifying in the end. Glad the semester's almost over. -- Mark Roberts - Photography & Multimedia www.robertstech.com -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
