Hi all, im looking to replace my Canon 50E film camera with a 50D or if I can reach it a 7D. My question is, is the auto focus speed in the body or in the lens. I like to take pics of military jets and will be getting a canon 100- 400 USM lens. Will there be any focusing speed difference in the 50 compared to the 7D ? Hope this makes sense. Thanks for any info, Jeff