Sunday, August 22, 2010

First try with High Speed Sync & Wireless E-TTL

Nectar Time

It wasn't my goal to shoot butterflies. I was going to shoot high school girls volleyball.

Unfortunately, the online schedule lied to me about the location of the game I was going to shoot, leaving me 35 minutes away from the action 10 minutes after the scheduled game start.

Where I was, had butterflies. So I decided to do some experimenting with Canon's 'Wireless' E-TTL exposure system.

I say 'wireless' because usually wireless means radio waves. Canon's system uses coded light pulses. Cheaper, I guess, than adding a radio transmitters and receiver to the flash, and certainly free of government regulation, unlike radio waves. But line-of-sight wireless brings certain unique challenges, and outdoors it can be real pain.

E-TTL is Canon's name for through-the-lens flash metering. The quick-and-dirty is that the camera has flash fire a short preflash, reads the scene, and then tells the flash how much juice to put out when it actually takes the photo a split-second later. This is generally a good thing.

Lighting: Canon 550EX to camera left, using Canon wireless E-TTL and high speed sync. Exposure was set about 2 stops above ambient. Master flash on camera set to no exposure flash. Shutter speed set to 1/500th of a second.

The good: solid, consistent exposures, despite constantly changing subject to flash distances. Rapidly changing subject to flash distances are the sweet spot for E-TTL.

The bad: it was a bitch chasing down the butterflies and having to adjust the master flash to point enough towards the slave flash to trigger it. This one place where radio waves have it all over line-of-sight systems.

High speed sync allows the use shutter speeds beyond the nominal sync speed of the camera, but it kills the action stopping-power of the flash. It also reduces flash power, a fact that becomes important shortly.

I lost several shots to the combination of the breeze, the tight magnification, my own unsteadiness and the butterfly's movements. While 1/500th of a second may be a good base for stopping action, in this case I needed at least 1/1000 of a second.

Unfortunately, at 1/500th each shot was already a full dump from the speedlight. Going to 1/100th would have mean moving the speedlight even closer to the peripatetic butterfly, which was not going happen given that I was using a 300 mm at it's minimum focusing distance already.

However, when my other 550 gets back from the shop, I can set up two flashes on the stand, and that should get the power level up to where I can shoot 1/1000th.

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