A friend of mine had a similar issue with his Canon 10D. His manually focused exposures were never quite on the money, but AF exposures were bang on target. After a suitable and similar round of measurebating, he concluded that the focusing screen was in need of shimming ... It was representing a focus plane some small fraction of a millimeter off from where the sensor was. Autofocus worked fine because it evaluates focusing distance through a completely different set of optics and parameters than manual focus.
He had his camera adjusted by Canon and now it focuses precisely, both in MF and AF. I believe they shimmed the focusing screen. Godfrey --- "Gonz" wrote: > I need some help with my *istD. For the longest time, I've been > having problems with my pics being quite soft wide open. I > thought that it was just because the lens was wide open. I have > alot of manual focus lenses, which I use often. The problem > showed up mainly with them, so I went back to look at some of the > pics more carefully, and I noticed a pretty consistent pattern. > There were areas of sharpness alright, but not where I wanted > them to be. I was consistently back-focusing. So I did some > tests. I mounted my FA* 85 1.4 on the camera, set it on a > tripod, and proceded to make some careful experiments to see if I > could put the blame where it belonged, on me or the camera. > > The setup was your typical measurebating focus test setup. I had > a ruler at an angle with a target off to the side of it where I > focused. I took pictures with and without autofocus. The result: > no matter how carefully I manually focused, the autofocus was > always right on the money, and I always back focused. I adjusted > the diopter after autofocusing to see if I could match the > camera's focus point, took my glasses off, put my glasses on, > danced around the camera, but no matter, I always back-focused. > What is going on here? Doesnt the autofocus see the same thing I > do? Or is something mal-adjusted somewhere? When I look through > the viewfinder after I auto focus, it seems to be in decent > focus, but it looks pretty much the same as when I focus > manually. If I then switch to manual focus and get it out of > focus and back in and take the pic, it is back-focused! Am I > going blind? ... __________________________________ Do you Yahoo!? Yahoo! Sports - Sign up for Fantasy Baseball. http://baseball.fantasysports.yahoo.com/