Here are a couple of teaser shots taken with the Bigma and my K10D over the weekend. It was the final round of the Tasmanian drift series.
The drivers were screaming out for photos so I got together one of each driver. Here are a few of them. I'll post some better shots once I sort through them.
I was experimenting with shutter speeds, started at 1/350, then to 1/250 and finally 1/180. That is about as slow as I can go hand held @ 300-500mm. I was getting 50%-ish hit rate at 1/180, but was getting better as the day progressed.
I will admit the AF system wasn't as quick as I would have liked, but then again I shot most at the long end which is quite slow. I did use a Circular Polarizer at the start of the day but losing that extra stop KILLED the AF speed.
No EXIF, but details are basically K10D, Sigma 50-500, Tv-mode 1/180-250, ISO 200. All are uncropped in-camera JPEG with only slight level adjustments in PS CS2.