EOS 3 focusing problem

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I've had the EOS 3 for 2 years now, originally with the 28-135 IS and also the 50mm 1.8 lenses. At all times pictures were sharp. I bought the 100mm 2.8 12 months ago, after selling my other lenses. Again, pictures were sharp. I recently bought the 28-70mm f2.8L and since using this lens am having problems with the focus.

While looking through the viewfinder, using AF and MF, the image is sharp as a tack. But when I take the photo, the result is less than sharp. What I'm experiencing is a shift in the point of focus (the in focus part of the picture is actually closer than the infocus image in the viewfinder!)

I believe the lens is fine, so I'm thinking that perhaps the film plane has shifted, if possible, or the electronic focusing has failed somewhere.

I've also been changing the focusing screen from time to time from the regular one to the split screen for manual focusing. Any similar problems from anyone? Any suggestions?

Thanks for reading.

action_photo_guy@hotmail.com

-- Michael King (action_photo_guy@hotmail.com), April 06, 2002

Answers

The AF of my EOS 3 works great and, moreover, I haven't heard of such a problem. Changing the screen to a split prism will effect metering--spot & evaluative don't work correctly--but it has nothing to do with AF.

Are you zooming after focusing? That may cause focus to shift. Is this problem present with other lenses? If so, get the camera checked out. However, since focus worked fine with your EF 100 2.0 USM and problems appeared with the new lens, it seems like you should get the new lens checked out.

-- Puppy Face (doggieface@aol.com), April 06, 2002.


If you switch out the focus screens often, they may not be seating properly. But does this only happen with the 28-70 and not with the 100mm? If that's the case, it is the lens or the lens/camera combination. In any case, you should contact a Canon service center.

-- Lee (Leemarthakiri@sport.rr.com), April 06, 2002.

Thanks for the responses. I took it to a camera guru, and it appears that the metal lens mount on the camera body has become marginally distorted (it is raised from the body a fraction of a millimetre at the top of the mount in comparison with the bottom section), which means the distance to the film plane has changed. Even though it's only marginal, it seems to be the reason for the problem. I'll take it to Canon ASAP and get it double checked and fixed.

Thanks again.

-- Michael King (action_photo_guy@hotmail.com), April 07, 2002.


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