New body / lens combo - difficulty focusing

[jerry12953]

Just starting to get to grips with my new Canon 7d and old (secondhand) 100-400 zoom.

I'm using the central focus point and recomposing where necessary, and Spot AF. Problem is, sometimes it just won't focus. I can point the central spot at a bird on a branch and it will sometimes focus in front or behind the bird, or on nothing; sometimes it will find focus but not lock on making it impossible to press the shutter.

Maybe I'm asking too much of autofocus? A wood warbler in spring foliage.....is that just too green on green for the AF mechanism to recognise the bird?

Most of the documented 7d focus problems seem to involve incorrect focus rather than no focus.

Any thoughts?

 

[magicaxeman]

Spot autofocus mode uses a very small area to focus on, it maybe that in low light or in situations where there is low contrast between the subject and the background that it struggles to lock on.
Try a different mode and see if that makes any difference.
I usually use one shot mode and the centre autofocus point, then recompose after locking focus.

 

[DaiTheDragon]

Have you tried using the distance switch on the side of the lens. If the switch is set to 6.5m and the bird is closer the lens can take some time to find focus.

Dai

 

[hollis_f]

See page 89 of the manual.

 

[buckas]

http://www.bfm.ee/wp-content/uploads/2011/01/Canon-EOS-7D-Owners-Manual.pdf

 

[49Clicks]

See page 89 of the manual.

Best piece of advice you can have, i have a 7D with a sigma 70-200 2.8 and found it was focusing badly.............. Take a read

 

[jerry12953]

P89 of manual is well thumbed....but thanks anyway.