Canon Autofocus

Started Oct 3, 2011 | Discussions thread
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BThomson
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Canon Autofocus
Oct 3, 2011

Hi, do quite a lot of wildlife photography and have been using the Canon 800mm f5.6 on a 1D MkIV body, which sounds just great doesn't it? The lens is indeed excellent but I have found major problems with the Canon auto-focus system! Basically, the MkIV is not capable of accurately focusing this lens! In fact it happens with other lenses as well. If the subject is in shade (even on a sunny day) or is less than mid-toned, I have found that I can't use max aperture (F5.6) because the depth of field is so shallow that the camera can't focus in 15 out of 15 frames! At other apertures, I need to fire off about 12 to 15 frames and then I might get 1 or 2 in sharp focus.

So I must admit that at times I would have to describe the auto-focus system as absolutely appauling. So when you look at those nice graphs of lens performance on the Canon website, bear in mind that they mean absolutely nothing if the camera can't focus the lens! Yes, I have fiddled endlessly with the micro-adjustments etc. None of these corrections can help a camera that can't focus!!! It's not camera shake or any other issue!

I posted this first in another forum by mistake, an in that I was asked to provide further details. So at the risk of a long posting - the focus issue happens in both modes (AI and One Shot) and it is most obvious when using a single af point where you are trying to get critical focus on a bird's eye etc. There are other problems as well, but I will leave them for now. There is nothing in any of this that makes me believe it is a faulty camera - it's more like a genuinely under-perfoming af system! So that's why I was curious to find out if others see this problem.

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