[Larne]

I have now had my new Sigma 70-200mm f/2.8 for a week and I am really struggling to come to grips with it. All the shots I shoot at 200mm f/2.8 seem to miss the target focus point; not by a lot, maybe by up to 10mm? Unfortunately sometimes it over-runs and sometimes it under-runs so I can't write it off as a back- or front-focus problem with the lens. Results at shorter zoom figures are better but the greater DOF is probably helping those and either way they are still not as crisp as I would like.

I know there must be a few of you who have this lens so I thought I would throw myself open to some advice. Is this user error? Is there something different I need to be doing to get the best performance from this lens? I am hand-holding it after all. Is this a common thing with these lenses that I should just be accepting - the performance is not bad, it just isn't 'perfect'.

Hints / tips / etc much appreciated.

[Dabhand16]

First thing is to eliminate (or not) camera shake. Try it on a tripod. Also, at the long end use 1/300th as a minimum for hand-holding, and faster if possible.

[Markulous]

Agree with Graham but also might be useful to have a couple of examples with EXIF, cropped in to show in/out of focus areas

[Larne]

I have just been out to shoot the two images below - tried to pick a subject that would show the problem. Both were hand-held and are 100% crops. I have not processed the images in any way (so no sharpening).

In both cases the black square shows where I focussed the camera.

#1 - focus appears to be on the bark behind the target


#2 - focus appears to be on the bark in front of the target


The images were taken one after the other and I didn't move, although I did (obviously) refocus the lens.

Thoughts?

[Markulous]

And you're using a single central focus point? Does look way out.

I'm guessing that your other lenses are OK which would only leave that lens as being the faulty item. Bizarre really as it's the camera that does all the real work of setting focus. I'd guess back to retailer/Sigma tho' probably worth emailing Sigma to ask for their comments/suggestions

[Sonsey]

Originally Posted by Larne

Thoughts?

How many focus points are you using? If it's all of them then the camera will normally autofocus automatically to a high contrast area which often isn't in the centre of the frame, this is very noticeable with the shallow depth of field you get when using f/2.8. If you are indeed using all the points try changing it to centre point only and test again (making sure you've also got the camera set to One-Shot autofocus, and you've got at least a 1/300sec shutter speed)....

...If your already doing that, then

[Dabhand16]

I wonder if the focus point had sufficient contrast to lock on properly compared to the rest of the image.

How about a couple using manual focus?

[Larne]

Grrr...


Put the lens on my 400D and it works fine. I guess I have never noticed the problem before as my only truly wide-aperture lens is my 50mm and that's broke. So most of the time I am shooting at f/4 or smaller.

So I guess that takes me to a new logical question...

Was the 10D known for poor focussing performance on low contrast subjects or am I looking at a faulty body?

[Larne]

This was shot at a range of about 4m with the focus point right over the eye. Again it is a 100% crop. Nothing wrong with the focus here methinks

[Markulous]

Nope! Looks good! So it's low light/lack of contrast shots the camera is struggling with? Certainly don't think it's the norm - will ask a pro I know who has one

[Larne]

Did a bit of browsing on the web and apparently the 10D did have a problem on some models with inaccurate focussing. At least so some people seem to be reporting.

Presumably you can still take a 5-year-old camera in to Canon to get it serviced? Anyone know of a link to their service centre in the UK - can't seem to find anything via the main site.

[Markulous]

https://self-service.canon-europe.co...70%26LANG%3Den