Lens Repair Question- Backfocus - DPChallenge Forums

Mattel Barbie Photo Designer Digital Camera

02/21/2005 10:03:19 AM · #1

I just discovered that one of my Canon lenses has a backfocusing issue. All of my other lenses focus perfectly with my 20D. Can this be repaired? Is it camera specific? Do they usually need to have the camera too?

Any insight would be great. Thanks.

nsbca7

02/21/2005 10:09:13 AM · #2

Call Canon.

And don't let them have the camera at the same time if you send in the lens or when it gets back it may not work right with the rest of your lenses.

Message edited by author 2005-02-21 10:11:03.

wkoffel

Canon EOS-300D Rebel

Canon EF 17-40mm f/4L USM

02/21/2005 10:21:59 AM · #3

I just had the backfocus fixed on my 300D. It was strictly a camera body issue. It manifested itself most obviously on my 70-200 IS, but it was there on other lenses as well. Are you certain that it's strictly with one lens?

And have you tried the obvious of cleaning all the contacts on the lens and EF mount? Always good to try before sending your baby to far away lands. :)

Tokina AF 12-24mm f/4.0 AT-X Pro DX

02/21/2005 12:05:57 PM · #4

Originally posted by nsbca7:

And don't let them have the camera at the same time if you send in the lens or when it gets back it may not work right with the rest of your lenses.

That was my thought. My 17-40 L (and other lenses)is tack sharp, so I don't want them to touch the camera.

What makes a lens back/front focus?

kirbic

Canon EOS R5

Canon RF 24-70 f2.8 L IS

02/21/2005 12:25:10 PM · #5

Is the lens that is back-focusing by any chance a "fast" lens, and are you having trouble mainly at larger apertures? If so it may be that you only really notice it with that lens, but there still might be a body issue as well.
I know that my 10D has moderate trouble with very fast lenses wide open, however the pain of having it serviced is greater than the potential benefit.

Beagleboy

Canon EOS-30D

02/21/2005 01:33:36 PM · #6

I just sent in my 70-200 f4 L that I had purchased used a few months back. I ran a bunch of tests with all the lenses I own and found this one to be the only one to be backfocussing. I also tested the lens using Jacko's 20D and got the same exact results. So I know it's not the body.

So off to Canon in Montreal it went last Thursday for repairs. They never asked me to send the Digi Rebel in with it. I am still waiting their call for the estimate.

02/21/2005 01:59:50 PM · #7

Originally posted by Beagleboy:

I'm going there now. I'll ask about yours. LOL!

LEONJR

Fujifilm FinePix S3 Pro

02/21/2005 02:13:22 PM · #8

What exactly is back focusing or front focusing? the camera doesnt focus correctly or .......? thanks

kirbic

Canon EOS R5

Canon RF 24-70 f2.8 L IS

02/21/2005 02:52:19 PM · #9

Originally posted by LEONJR:

What exactly is back focusing or front focusing? the camera doesnt focus correctly or .......? thanks

Yes, back or front focusing is when the camera/lens combination repeatably focuses in back of (or in front of) the focus target. It's not that easy to identify, since there are a lot of variables. It's particularly difficult to figure out whether it's the body or the lens, or both.
It is not at all uncommon, but a lot of the reports you see are due to user error. It takes a bit of careful, structured testing to nail down a problem.

riot

Canon EOS-1D Mark IV

Helios 40-1 85mm f/1.5

02/22/2005 06:45:47 AM · #10

Originally posted by LEONJR:

What exactly is back focusing or front focusing? the camera doesnt focus correctly or .......? thanks

//homepage.ntlworld.com/dltucker/nikond70/faqs_backfocus.html tells you a lot about back/front focus...

Also //www.dpreview.com/reviews/canoneos10d/page19.asp has a very good visual explanation of back focus, if you scroll halfway down the page.

mikeholleman

Canon EOS-20D

02/22/2005 03:55:48 PM · #11

I sent my new 20D to the factory and it came back with same issue on my 24-70mm 2.8L. They then wanted the body and lens, so I sent them along with my new 70-200 2.8 IS (which focused perfectly) just to be sure they all worked. John at Factory in NJ explained that all adjustments are within factory specifications, so there should not be an interchangeability problem. I was a little sketical, which is why I sent all. I am waiting on the repaired products and expect them by the end of the week. If you want to talk to John here is his info:

John-Canon Factory
732-521-7886
jdimauro@cusa.canon.com

LEONJR

Fujifilm FinePix S3 Pro

02/22/2005 03:57:32 PM · #12

thanks riot, and kirbic i had never heard of that now i wonder if its a problem that can be on a zoom lens camera not a slr i'll have to do some research thanks again