Originally posted by roentarre For the motor car racing, DA 50-135 might be of better choice for faster autofocusing (not that people really use autofocus during motor sports photography)
For these it seems like trap-af would be mighty useful, but it is my understanding that AF lenses w/o MF switch on the lens can't use trap-AF (and the sigma 70-200/2.8 MF switch didn't decouple the focus mechanism w/ the body, but just coupled it to the focus ring so tit doesn't actually work).
If I had a MF lens or shorted out the contacts, would the body be fast enough for a race to trap-AF some shots?