One of my 10D lenses is starting to front focus??

[CyberDyneSystems]

I have shot about 13,000 images with my 10D in the last few months,. at no point did I feel I had a focus issue untill very recently.

I have done no actual "tests" involving rulers etc.. but I feel I know th ecamera well enought to be sure that a problem has developed.

My Sigma 70-200mm f/2.8 EX seems to have gone all front focus on me. I can see the eefect clearly in the viewfinder as I take the photo,. I find that I need to manual "tweek" the focus ring every time to keep the subject in focus. I nee to do this in singe shot AF as If I am in AI focus or servo,. the camera will fight my instincts and continually retune the the focus untill I am front focusing again.

This only seems eveident with teh one lens I mention.

Is it really happening with all my lenses but with there smaller apertures the depth of feild increas makes it so I can no longer see the difference in the viewfinder? If is "wide open" at f/6.3,.. is there ANY way at all to test such a thing?

And one of the oddest things is that I KNOW this was not allways the case. I have hundreds of photos I have taken with this lens, the fashion show in my gallery are examples,. that display no focus problems.

So,.. here are my questions.

1. Is it possible to test these small aperture lenses.

2. If it is only the one lens,. can Sigma adjust the lens?

3. If it IS all of my lenses, will Canon adjust the 10D even if the lenses aren't Canon?


As I said,. I think I need to do some more concrete tests to be 100% sure,. I'll need to "shoot some rulers" but I know ths camera well enough to know that something has definately changed.

[CyberDyneSystems]

Oops,.. my mistake,. it is back focusing, not front focusing.

[perfectpixel]

CyberDyneSystems wrote:

And one of the oddest things is that I KNOW this was not allways the case. I have hundreds of photos I have taken with this lens, the fashion show in my gallery are examples,. that display no focus problems.



Are the photos in that gallery posted at 100% resolution, or are they cropped and enlarged?

I have a similar experience as wyou with the 10D: with a 28-135 IS I thought the focus was off, so I tried a Canon L len$e and the results were much better.

[lightandlife]

CyberDyneSystems wrote:
1. Is it possible to test these small aperture lenses.

2. If it is only the one lens,. can Sigma adjust the lens?

3. If it IS all of my lenses, will Canon adjust the 10D even if the lenses aren't Canon?


1. I think so. With smaller aperture, any autofocusing problem will be less visible, but it will be discernible. Post some test shots without cropping, using the central focusing point.

2. There are three possibilities.
(a) First determine whether back/front focusing problem occurs only with that Sigma lens. If it occurs with any other Canon lenses, it is 10D that is culpable.
(b) If other normal 10Ds have no problem with your Sigma lens, then your 10D is guilty. However, this test would be difficult to perform unless you have lots of photographer friends in your area.
(c) Interface problem. Your 10D may be normal. Sigma lens may be normal (with other cameras), but they may not work properly together.

3. If it occurs with all your Sigma lenses and not with any Cannon lenses, it is the interface problem above. You can still ask Canon to adjust it for Sigmas, but when it is fixed, you may have problems with other Canon lenses. If you use any Canon lenses, you may not want this option.

[CyberDyneSystems]

Thanks lightandlife,

I do have Canon lenses as well,.. including a 17-40mm "L",. so I do not particularly want to alter the 10D,. especially as I am only seeing the problem in the one lens. But I do need to get more scientific in my methodology and prove to myself it is only the one lens before I make any deceisions.

unstuck,

The photos in my fashion show gallery are not cropped,.. just reduced in dimension and compressed as jpegs.

also last night I palyed with the lens agin,. in my apartment with incandescant light,. just like the fashion show,. and it seemed fine. But the last few times I have used it it was outdors,. at or after sunset (so no harsh light) but those times the backfocus was CLEARLY visible through the viewfinder?