Tuesday, August 15, 2006

Photography stuff I learned yesterday

Yesterday Ben and I got on the subject of flash photography. (In my humble opinion, photography has about as much in common with flash-photography as snow skiing does with rodeo-clowning. Anyawy...). We started discussing high-speed synch flash work. I explained how I *thought* it worked, but had to admit...I had no proof to back up my idea. So I did some Googling[tm] and came up with the following web site. It seems to explain the reasons I wasn't happy with many of my Wednesdays @ Wakefield mountain bike race photos. For many of them, I was seeing blur in the riders, so I'd up the shutter speed (beyond the 1/250 synch speed). Instead of freezing the action more, it actually blurred it. I never really *got* why until now.


This site offered some nice insights that I thougth I'd pass along. The most important points of the site (for me, anyway) are:

"...there is a somewhat widespread misunderstanding that high speed sync would be useful for stopping motion in action photography. Since it's called "high speed sync", it seems reasonable on the surface to presume that it would be good for photographing objects moving at high speed. But this is not the case. "


"With ordinary flash, the first curtain of the shutter opens fully, and then the flash electronically turns on and off, faster than any mechanical shutter could possibly open and close. Finally, the second shutter covers up the film."


"The problem with "high speed sync" for action photos is that it works by making the flash slow down. Since the camera's shutter can't open fully in less time than its max normal sync speed, the film can't be exposed all at once at high shutter speeds. Exposure must be controlled by the shutter's slit traveling across the film, exposing different parts of the film successively. Instead of giving one almost-instantaneous burst of light, the flash gives a sequence of many pulses of light, approximating a continuous light source during the time the shutter is open."

So there you go. A 2 minute primer on high-speed synch flash photography. Hope you enjoyed it.