I'm not sure why you're trying to use AI Servo on a stationary subject; it's
intended to be used on MOVING objects.

Read here: http://photonotes.org/other/ai-servo.html

and note the first sentence in the conclusion "was designed to function as
the finest central-area autofocusing system in the world for moving
subjects".

It's also not clear which AF points are active on the cameras you're testing
with. Is it 35 points on a 1-series, or a single center point, or something
in between? From what I've read, I don't think there's a problem with the
lens.

Tom P.


> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of 
> Joerg Thomas Klein
> Sent: Tuesday, January 10, 2006 12:31 AM
> To: [email protected]
> Subject: Re: EOS focus hunting on 70-200
> 
> > Servo mode needs a subject to be locked on, and bland 
> subjects of low 
> > contrast are not good for that.
> 
> I used a tripod and was shooting a traffic sign in white and 
> blue. On a second try I shot some tree branches against the 
> sky. In both times the image in the viewfinder is sharp but 
> the af is hunting like he could not find the right tooth of a 
> gear wheel.
> My problem is that I would like to buy this lens as an 
> replacement for a old Sigma 2,8/70-210 APO which does not 
> have this problem, but is not usable on a the 350D.
> If I need to pay some money to repair the Canon 2,8/70-200 
> the I would give the lens back and look for another one.
> 
> Thomas

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