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Hi all

I'm just breaking in my new EOS70D and have a question for any of you guys who use Canon models with the fancy autofocus area choice.

Which of the three AF area choices would you normally use when spotting?

I've tried with Auto but, in particular on approach shots (aircraft nose on at approx 45 degrees) there seems to be a distinct lack of sharpness on the front and rear of the aircraft.

I wonder if I should be using the Zone AF setting (central zone selected?) for better results.

Lens used is the Canon 70-300mm f4-5.6 IS USM which I've been using on my 400D for the last five years with no issues.

Ideas appreciated.

Thanks.

What is your aperture setting?

I'm not sure I've used a camera with these sort of autofocus zones. But on all my cameras - 1000D, 50D, and 5D2, I've only used the centerpoint for focusing.

It's not that the other ones may not work well (I don't actually know); it's just that I want to know exactly where the camera is focusing.

graphic wrote:What is your aperture setting?

Same as most folks, I guess, I try to keep it as close to f8 as possible but generally no lower than f5.6 and no higher than f10.

Huh. F8 should give you enough depth of field that it wouldn't really matter what part of the airplane the autofocus is snapping to.

My 70-200 f2/.8 is notorious for focusing on only half of the aircraft, even when shooting at f/8.

graphic wrote:Huh. F8 should give you enough depth of field that it wouldn't really matter what part of the airplane the autofocus is snapping to.

Agreed. In fact, I shoot wide open most of the time (F5.6 on the 100-400, F4 on the 70-200), because the lenses are plenty sharp and DOF is never an issue when the aircraft is 600+ feet away. It's more worth it to be able to decrease the ISO.

CO777ER wrote:My 70-200 f2/.8 is notorious for focusing on only half of the aircraft, even when shooting at f/8.

You sure it's a DOF or focus issue? My 70-200 has a sporadic issue where it will get very soft on the left 1/3 of the frame. But I'm 99% sure it's a lens element issue.

I've got the Hamburg Airport Days trip coming up next weekend so think I'll go with centrepoint focusing and maybe allow the aperture to drop a little.

Thanks for your input, guys.

Small steps.