I've had trouble getting tack sharp images with my 50D on any shot where the main subject is several hundred yards away or more. Subjects closer than that distance (flowers, birds, etc) I've been able to get tack sharp images. I believe my techniques are sound (tripod, adequate shutter speeds, mirror lock-up for static subjects, f/8 to f/11) and my tack sharp up-close images seem to verify this. I've found that this issue is true for my telephoto lenses as well as my wide angles lenses. As the result of a tip, I recently began using manual focus on my landscape images using Live View at its 10x magnification. The results have been splendid; tack sharp images consistently. While I like the result, it saddens me to think that I cannot rely on the 50D autofocus for farther out shots. I have not checked the different lenses to see if a microadjustment would help, because that would only throw off the autofocus on the up-close shots. Has anyone encountered this besides myself? I'm unsure what to do now when I'm trying to shoot wildlife in their environment (ie moose with a mountain backdrop) since there may not be time for Live View mf and I'd like to be able to use af. Any thoughts would be appreciated. Thank you.

