Strobist - off camera flash challenge

Because he wanted to be sure to nail the shot.

The room was very dark and the flash was fast. So the idea is that if the flash didn't go off the whole frame would have been black. no matter how long the exposure is, you will only see something when the flash will light. Then the next step is to find a way to have your flash sync with the hammer swing. As described in the notes, he used a self-built sound trigger. So as soon as the light broke, the flash triggered for a short time and that's the results.

Using a fast shutter would need either a very fast frame rate to not miss the shot or a perfect synchronization.. you could waste many light bulbs that way.