Canon autofocus at f8

slimrbp · #1 (**permalink**) 12-09-2010, 09:19 PM

Hi,

I made an interesting discovery today and thought I would share it as it was news to me.
I have been experimenting with a 2x extender on my Canon 300mm f4, the maximum aperture of f8 meant that autofocus didn't work (I did try taping pins). I am ok with manual focus but my hit rate wasn't that great

.
Anyway, to cut a long story short autofocus works in Live View using the 'Live Mode' AF.
It's not the quickest way of focussing but I did find it to be accurate most of the time as long as I put the focussing point on a detailed area.
This was on a 7D.

JeffH · #2 (**permalink**) 13-09-2010, 07:19 AM

That's interesting - must give it a try. Thanks Richard

Jeff
(Schedule 1 Licence holder for Kingfishers, Barn Owls and Avocets)

MeadsMan · #3 (**permalink**) 13-09-2010, 07:13 PM

Strangely I found this out using video on my 7D with the 400mm prime and 1.4 converter,it never entered my head to try it as you suggest with stills photography,it`a a good tip.As you say it`s a little on the slow side,I am guessing the better the light is the quicker the focusing may work.Thanks for the heads up.