Back focussing issues


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Zack

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Oct 20, 2004
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Does any one know how much does it cost to repair a lens which has back focussing issues in Canon service center?

Assuming that warranty has expired.
 

Jemapela

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Logically, this probably depends on the lens you bring in.

Not to deliberately go off-topic, I would like to share a very recent experience at Canon S'pore Service Center for a lens I brought in for repairs due to autofocusing problems on my 20D (which didn't seem to happen before I got my 20D).

This lens, EF 28-105mm II USM, occasionally doesn't focus properly. It would "lock on" far off the aimed subject and allow the 20D to shoot when it should not (because there's focus priority). I didn't really observe if it tended to be back or front focus but I was pissed with a severely blurred out-of-focus viewfinder image and my 20D indicating "locked on and ready to fire" (green LED steady lit).

According to the Canon technician, she changed an IC board in it and also changed the thickness of the lens mount (by replacing the steel mount) for reasons she explained but I didn't fully understand (ehh.. who can anyway?) The initial estimate of about $90 was upped to a $160 repair bill.
 

Zack

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So I should bring the lens and body together for them to check?
 

Jemapela

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Zack said:
So I should bring the lens and body together for them to check?
I guess it's better. No harm anyway.

If you are sure it's the lens, then just bring the lens.
 

donkuok

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Oct 11, 2004
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Zack said:
So I should bring the lens and body together for them to check?
you ought to bring both lens and cam. the canon service centre will need to test them separately or exclusively.
 

santoarmand

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Jun 1, 2005
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I think I might have the same problem. I'm using 350d and most of my lenses are 3rd party and I only have 50mm 1.8 and 18-55 kit lens canon brand. I found that my tamron 28-75 is not as sharp and it supposed to be, but since it is sharp enough for me I just accept as it is.

Recently I just bought 2nd hand sigma 70-200 f2.8, and this time I really found it to have front focus seriously at 200mm with distant object. However testing with Sigma service center with their camera reveals it have a perfect focus.

Does anyone know if front focus/ back focus issue becomes more prominent with tele lens, large aperture, and distant object?

Does anyone know how to bring up the issue with 3rd party lens? Canon Service Center will surely says that it's the 3rd party lens got problem.

donkuok said:
you ought to bring both lens and cam. the canon service centre will need to test them separately or exclusively.
 

USM

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santoarmand said:
I think I might have the same problem. I'm using 350d and most of my lenses are 3rd party and I only have 50mm 1.8 and 18-55 kit lens canon brand. I found that my tamron 28-75 is not as sharp and it supposed to be, but since it is sharp enough for me I just accept as it is.

Recently I just bought 2nd hand sigma 70-200 f2.8, and this time I really found it to have front focus seriously at 200mm with distant object. However testing with Sigma service center with their camera reveals it have a perfect focus.

Does anyone know if front focus/ back focus issue becomes more prominent with tele lens, large aperture, and distant object?

Does anyone know how to bring up the issue with 3rd party lens? Canon Service Center will surely says that it's the 3rd party lens got problem.
Dude, that's the reason why Canon always ask you to buy original. If you have problem with a 3rd party lens on a Canon body, you have to pay for a service rendered no matter whether the problem lies with the 3rd party lens or the body.

Canon will not calibrate your 3rd party lens on a Canon body.
 

grantyale

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Oct 4, 2004
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You can send in the body and ask for a 'best autofocus' calibration. Those canon guys have all sorts of tools by hand...
Note that if you request for an AF calibration or check of backfocus, they may tell you the body is 'within specs'. That's why you'd need to be more specific, and tell them it shows up with bright tele lens if necessary. The calibration requires electrical adjustments, charge is 63 dollars.
 

santoarmand

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Jun 1, 2005
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Ahaha, I'd like to get myself Canon 70-200 IS f2.8 L if I'm making money with my camera. But as of this moment, I'm just poor hobbyist that can only afford 2nd hand 3rd party lens.

Oh btw, I've checked with sigma that their recent lenses already comes with rewritable chip. So what they need to do if there is back/front focussing complain is to use the particular user's camera, take photo with their calibration chart, translates it into correction factor, and dump it back into the lens chip. Too bad my 70-200 is not the new DG version, hence there is a need to change the whole PCB board.

USM said:
Dude, that's the reason why Canon always ask you to buy original. If you have problem with a 3rd party lens on a Canon body, you have to pay for a service rendered no matter whether the problem lies with the 3rd party lens or the body.

Canon will not calibrate your 3rd party lens on a Canon body.
 

santoarmand

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Jun 1, 2005
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Some update on my focussing issue with Sigma 70-200mm f2.8. It seemed that:
1. The lens is focussing right at the dot when viewed from viewfinder with focus test chart
2. However when the image is viewed, it shows serious front focus issue

I'm using tripod with internal flash, 200mm, 1/100s, f2.8 to test it out with 2 meter distance from the chart. Can I say that it is the calibration of the CMOS sensor that is having problem since it focus nicely on the viewfinder?

Any insight from the pros?
 

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