Canon 300mm f4 focus issue

pecrow

pecrow

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On a couple of occasions recently, when i first start shooting, the lens won't autofocus at all. i can hear the IS motor spin up but no af motor noise. No focus attempt at all. If i then focus it manually and switch back to af, it behaves normally. It'll then be ok all day.

When its playing up, switching af or focussing modes doesnt help, nor af on/off and i've cleaned the contacts. it's random but the only thing thing that cures it is to manually move the focus ring.

Before I send it off to Canon, I'd be very grateful for any suggestions as to what may be amiss.
 
If the focus is miles out with a long lens, like set to infinity when you're trying to focus something close, the AF doesn't know where to go so does nothing until you give it a nudge in the right direction. All I can think of before you send it off.
 
For 7D, I believe you can enable AF search in custom menu.
 
Last edited:
HoppyUK said:
If the focus is miles out with a long lens, like set to infinity when you're trying to focus something close, the AF doesn't know where to go so does nothing until you give it a nudge in the right direction. All I can think of before you send it off.
Click to expand...

i'm sure its only started doing this recently though
 
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