service lens or body?

[desantis]

I've got a puzzler that perhaps someone can help me with.

 

I've had my 70-200 f4 since 2002 with no problems. I recently got a 30D. The

70-200 when mounted on the 30D noticeably backfocuses. I have 3 other lens: an

50mm f1.8, 20mm f2.8, and a 200mm f2.8. None of these exhibit back focus on

the 30D that I can see.

 

So the problem's with the lens right...?

 

not exactly, when I mount the 70-200 on my old Elan 7, it focuses just fine.

For the record I test focus by pointing the lens at something at infinity focus

and then look at the distance reading on the lens. On the 30D the focus point

is beyond infinity and the image is slightly out of focus, on the Elan the focus

point is right on infinity and the focus is sharp.

 

So this make's it seem like the problem is with the 30D. But that doesn't

explain why the other 3 lenses would focus just fine.

 

Canon tech support says just send both the 30D and the lens in, but I'd like to

avoid the hassle of sending both. Any ideas on where the problem is?

 

Greatly in your debt,

 

Angelo DeSantis

[jimstrutz]

I think you will need to send both in to get this fixed right. I would also send in one of the other lenses that works right with the 30D, but that's just me being paranoid.

[glenroy]

I have the 10D and 20D and EOS 3. My 24-70mm overfocuses on the 20D. Spoke to Canon Australia and I have to get the lens re-calobrated to that camera. They also need 2 other canon lenses at the same time to check with them. It should be done free of charge.

 

Good Luck,

 

Glen

[steve_dunn2]

<p>There are a lot of previous discussions of front- and back-focus problems, and you'll find that it's the combination of the lens and the body; your situation of having a body which works fine with some lenses but not others, yet those lenses work fine on other bodies, is not atypical.</p>

[desantis]

Thank you everyone. I guess that answers my question. I'll search the forums for information on that topic. Did they ever resolve this apparent paradox? Is there something specific to the camera or the lens that would cause this seamingly random problem: lens speed, camera focusing system, how fast the lens focuses on certain bodies?

 

Thanks again,

 

Angelo