I tried some off camera flash at yesterday's local DH race. Setup: Canon EOS 10d, EF 24mm/2.8, Sigma EF500 DG Super flash. Sigma in manual slave cell mode fired by the 10d's onboard flash. I like the first one a lot, although it should have had a slower shutter speed. Just couldn't use longer as there was a bit too much ambient light. What do you think? Also two different crops of the second image, i do like the vertical a lot myself, such a pity it takes down the resolution quite a lot...
I gotta say the slave cell doesn't work 100% well as I'd want it to. I'm thinking of getting a 10m (30ft or something?) sync cord next...