7D in low light and AI servo

AKHOO wrote in post #11084374
=AKHOO;11084374]I had a similar problem with getting the 7D to lock onto a subject using autofocus. I didn't immediately realise it was a setting I had made because it was only a problem with my 135L. I had no problems with the 35L/85L locking/tracking a subject.

I literally had to guide it - manual focus to around the correct distance then it would lock on. If the subject was a 1.5 metres in front of camera, but the lens was at infinity, it would not lock, and vice versa.


The problem setting was the AF Search function on the 7D. Changed it and it started working.

I shoot a lot in low light/high ISO using my 50D/135L in AI Servo.. I've never had any problems locking focus.. I believe with the 7D/135L you should be even more successful..

yogestee wrote in post #11086495
I shoot a lot in low light/high ISO using my 50D/135L in AI Servo.. I've never had any problems locking focus.. I believe with the 7D/135L you should be even more successful..

This is what I am referring to with the 7D settings.

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Content has been taken from: http://www.garyluhm.ne​t/bio/tips_0310.html

Custom Function III-4. Lens drive when autofocus is impossible.

Sometimes when the subject is wildly out of focus (OOF), a camera can’t find it, and the bigger the telephoto, the more likely this is. For the wildly OOF subject, the default (0) setting will go hunting for it, focusing in or out until it finds focus. Since this takes time, with the lens potentially going on a time-comsuming chase for focus, option (1) stops focus, which means you must re-find it manually, bump/ try again (which often fails), or focus on something other than the subject, and then sort of coax it in.

I used the stop (1) setting for a while. It works if you know the approximate distance of your subject, and pre-focus. For BIF, guess the bird's flight path, focus on something close to that distance, and—when the bird flies—hit the focus when you’ve got the bird on the point. For setting (1) to work, you need to be vigilant.

I’ve switched back to the default (0). I still pre-focus, but now if I lose it, I’ve found it gets focus back faster by hunting for it. I find this especially useful shooting hand-held, where you'd need a third hand to easily focus manually with a 500mm f/4 (and this is often my situation in a kayak). When on a tripod, it’s easier to manually get the focus close, and then bump the focus to accurately acquire it, so a stop (1) option may make some sense."

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I had mine set to Focus Search Off. Because the lens was focused at say 1.2m (for example) and I wanted to focus on a subject that was 10 metres away, it would simply go there is nothing at around 1.2m to focus on so I won't continually hunt for something that is not there. However, if I pre-focused to the approximate distance, for example 9 metres, then the autofocus would work. I have since set this back to Focus Search On.

The point that I am trying to make is this is most likely a settings issue and that there is nothing wrong with the camera. The onus is on you to tailor the 7d to your requirements.

I can't get it to AF even at f1.4 in the dark

Switching to single point with expansion, or sometimes even zone AF, may make it work, since there are more possible AF points to pick something up. You loose a bit of precision in selecting where to focus, but compared to not at all, it may still be to your advantage.

Just out of curiosity, what sport(s)?

In-the-dark football (or soccer in Americanish). What the Norwegians call "nollkolleboll".

No problems here. Low light action is the main reason I bought the 7D, and I'm very happy with it. The lens used can be a big factor in AF performance. The 70-200 F2.8 and 17-55EFs have performed very well for me.

apersson850 wrote in post #11087737
Switching to single point with expansion, or sometimes even zone AF, may make it work, since there are more possible AF points to pick something up. You loose a bit of precision in selecting where to focus, but compared to not at all, it may still be to your advantage.

I agree with Anders. I think you should try AF expansion rather than single point.

Tim