I noticed a strange phenomenon Friday night while shooting a high school soccer match. I was using my 1DMKII, EF70-200MM F/2.8 L IS USM and EF 2xII Extender. I was shooting pre-game activities and we still had bright sunlight. I had set Av mode, f/5.6, ISO-200 and was seeing 1/500 and faster shutter speeds. As always, the use of the extender was slowing autofucus a bit andI noticed some real difficulties when the players were backlit. This problem was bad enough that I wasn't getting anythingof use.


To this point, there's no story. We know that extenders slow theautofocus performance and that shooting into the setting sunis difficult at best.But there is more. My daughter is shooting the same game and she asks for the 1D body so she can shoot withmy EF24-70 F/2.8 and get some wide angle shots of the playersstretching. So, I switch the EF70-200 and extender onto my XTi and go back to shooting warm-ups. This is a rare comparison, because I don't usuually use both bodies at the same event.


The odd part is the hit rate with the XTi was far better and the autofocus faster than with the 1DMKII. I shot about 40 more frames before dumping the extender and setting up for the game. I'm prone to complaining about the weight of my1DMKII, but not about it's performance.


So,anyone else have experience with both bodies and any reason to believe the XTi should outperform the 1dMKII with this combination?


I have a playoff game tonight and I'm going todo a back-to-back comparison of the combination again to see I can duplicate the performance difference.