40d focus problem

[Wayne Fox]

In doing some testing with my 40d and 3 other bodies (5d, 1DsMarkII, and 30d), my 70-200 f/2.8 lens will not focus correctly at any focal length on the 40d ... though it confirms focus it is slightly soft.  I have verified this using live view 10x to focus (a feature I really like btw), the resulting image is always sharper.  The lens seems to focus fine on the other 3 bodies, and other lenses on the 40d seem to be focusing ok (still testing that).

I've never had an experience with front focusing, but I'm puzzled by this.  It seems if the body was the problem, all lenses would be an issue, and if the lens was a problem, it would be a problem on all bodies.

Anyone with thoughts or experiences that might cause something like this?

[Jonathan Wienke]

I've never had an experience with front focusing, but I'm puzzled by this.  It seems if the body was the problem, all lenses would be an issue, and if the lens was a problem, it would be a problem on all bodies.

Doesn't the 40D have a by-lens focus calibration adjustment feature? If so, it might be incorrectly set for that lens.

In more general terms, focus calibration is determined equally by body and lens. A back-focusing body and front-focusing lens will cancel errors and focus correctly. It could be that particular combination has lens and body errors both in the same direction so they add instead of canceling out.

[meyerweb]

Doesn't the 40D have a by-lens focus calibration adjustment feature? If so, it might be incorrectly set for that lens.

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Nope, only the 1D MkIII (and, I assume, the 1Ds MkIII)

[macgyver]

I don't think I have noticed anything with my 40/70-200.

[Wayne Fox]

Just as a note, I have tested 4 40d bodies to this point, with 1 70-200mm lens and with 2 24-70mm lenses.  (all 3 lenses on all 3 of the bodies).

My body (very early model, received well used from canon before the camera's were released although supposedly not pre-production) and my dealers floor demo performed the same.  10x focusing with live view with somewhat distant targets was noticeably sharper than anything with autofocus.

A new body we took out of the box at the camera store performed better, but still did not nail focus with any of the 3 lenses at various focal lengths.

Another new body out of the box I tested today seemed to be very close, but I didn't actually have time to shoot it, just check it out with one lens on a tripod quickly before leaving my office.

At this point I'm not sure what to think, other than I wish I could use live view to focus my landscape work with all my camera bodies. I know if I decided to actually keep one, I'll be doing this to decide which body to pick.

[Ken Bennett]

Canon Service can adjust a specific camera and lens together to provide better AF. You need to send in both pieces, and ask for "best possible focus." If you are a member of CPS this is pretty straightforward (and I would call to see if it could be done under warranty).

Last summer I sent my 70-200/IS and one of my 1D2 bodies for this adjustment. Like you, my photos were just a little out of focus -- enough to be maddening, but not enough to notice while I was shooting. As it turned out, they were both out of factory specs, and a basic overhaul fixed the problem. (I didn't need the "best possible focus" thing done, in other words.)

--Ken