Servo AF Mode on my 5D

[Ed Blagden]

I feel almost embarrassed asking this question - after all I have been using Canon EOS cameras for more than 10 years so I really ought to have nailed this by now.  But I haven't.

My problem is, when I put my 5D in AF Servo mode to track moving objects (most recently runners coming up to the finish line at a school cross country event) I can almost never achieve good focus.  And I'm not even aiming at tack-sharp here, just reasonably OK for a 5x7 print would do fine.  I reckon my success rate is less than 1 in 20 shots, the other 19 being unacceptably OOF.  It is hard to tell, but it looks to me like the focal plane is somewhat behind the moving subject.

My typical setup when I'm using AF Servo mode is my 5D, centre AF point only, lens is a Sigma 70-200 f/2.8 HSM, subject about 10 - 20m away coming roughly towards me, I usually shoot at f/4 for this kind of situation.  I get the same issues with my EF 85mm f/1.8 and my EF 24-105 f/4L Zoom.

I don't think my camera is the issue - I remember having similar problems with my old EOS 3 and EOS 5 film cameras.  And all the above lenses are tack sharp when I shoot in One-Shot mode (which I do 99% of the time).  So I don't think there is anything wrong with my lenses.

So what am I doing wrong here?  I think it must be my technique, but I'm baffled.  Any hints?

Ed

[Frodo]

I feel almost embarrassed asking this question - after all I have been using Canon EOS cameras for more than 10 years so I really ought to have nailed this by now.  But I haven't.

My problem is, when I put my 5D in AF Servo mode to track moving objects (most recently runners coming up to the finish line at a school cross country event) I can almost never achieve good focus.  And I'm not even aiming at tack-sharp here, just reasonably OK for a 5x7 print would do fine.  I reckon my success rate is less than 1 in 20 shots, the other 19 being unacceptably OOF.  It is hard to tell, but it looks to me like the focal plane is somewhat behind the moving subject.

My typical setup when I'm using AF Servo mode is my 5D, centre AF point only, lens is a Sigma 70-200 f/2.8 HSM, subject about 10 - 20m away coming roughly towards me, I usually shoot at f/4 for this kind of situation.  I get the same issues with my EF 85mm f/1.8 and my EF 24-105 f/4L Zoom.

I don't think my camera is the issue - I remember having similar problems with my old EOS 3 and EOS 5 film cameras.  And all the above lenses are tack sharp when I shoot in One-Shot mode (which I do 99% of the time).  So I don't think there is anything wrong with my lenses.

So what am I doing wrong here?  I think it must be my technique, but I'm baffled.  Any hints?

Ed

Try enabling the expansion of the AF point activation area using custom function 17.  This will bring the six "hidden" central AF points into play and assist focus tracking.

Cheers

[Ed Blagden]

Try enabling the expansion of the AF point activation area using custom function 17.  This will bring the six "hidden" central AF points into play and assist focus tracking.

Cheers

Thanks!  I'll try that.  Also, should I select the centre AF point only, or should I allow auto selection where the camera gets to choose between the 9 points?  I never use the latter setting for normal shooting as I want to choose the focal point myself rather than letting a computer do it for me.  But does it make a difference when in AF Servo mode?

Thanks

Ed

[Atlasman]

Try enabling the expansion of the AF point activation area using custom function 17.  This will bring the six "hidden" central AF points into play and assist focus tracking.

Cheers

I shot an entire hockey tournament with the hidden points (in servo mode) and got excellent resulst.