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March 11, 2006
How to Take Photographs in a Lecture Hall
At least, here's how I took these. The camera body doesn't matter. Any camera body can fire a flash and take pictures at a 1/100 second shutter speed. I've got fifty year-old double-reflex cameras that can do that. A bounce flash with a high guide number was the moneymaker on these. In this case a Nikon SB-22s, guide number adjustable up to 92. 
I was manually controlling exposure by adjusting the amount of light the flash put out and rotating the flash head up and down. I pointed the head up, or in some cases up and slightly forward. The basic idea was to bounce the light off the ceiling, which was thankfully white. The lens was on f4, the sensitivity of the CCD was ISO 1600, and the flash was set to ISO 1600/f32. That is, if the flash head was pointed straight forward, I could have taken these pictures at f32. Instead I was taking pictures at f4 because the ceiling was high, so there was a lot of dispersion on the way up, I lost a stop as the light bounced off the ceiling, and then it dispersed more on the way down. I was literally sending 32 times more light out with each picture than I would need if the flash was straight. Don't be confused by f32 and 32 times. The 32 times comes from 26, or 6 stops of exposure value difference between my lens and my flash (f4-f5.6-f8-f11-f16-f22-f32). The two occurances of 32 are coincidental. The advantage of all that dispersion and bouncing was using the entire ceiling as a huge soft light source, so the shadows are soft, instead of harsh, there's no red-eye, blown out highlights, any of the stuff most people expect from flash photography. A medium telephoto zoom, in this case a Nikon 70-210mm/f4 was also helpful to get through the mess of microphone stands and speakers, and control the messy background by only selecting a small amount of it.
Posted by Niels Olson at March 11, 2006 11:10 AM
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