Am having occasional difficulty with focus on Canon 70-200 F2.8 IS lens .. any suggestions ?

[ian_luyt]

I am having difficulty achieving focus on the right subject (or on the right

part of the subject) with this lens. It often picks up something on the edge

of the composition. Any comments or suggestions on how to correct this ?

[mike_kim]

Which camera are you using?

[jwhite3.0]

What's your focusing distance and the aperture used? Close-up and at f/2.8 can require practice especially if you're not using center point AF. One-shot mode? AI Servo?

[joewoo]

Each lense has a minimum focusing distance... U have to be X meters away...

 

If u take a look at the lense, on the side there's a switch... X-infinity...

 

Pick the smaller one... If you're still having focusing problems, then you're too close to the subject and u have to back up...

[leopoldstotch]

Do you have one of the edge pocus points selected? Its not hard to forget about if you change it.

[leopoldstotch]

...That "p" should be an "f" in "focus".

[keith_lubow]

I think we need to know more about how you have your autofocus set up in order to help. Which mode, and which point/s? (And just for the hell of it, which camera?)

 

Keith

[lee_smith2]

And what were you focusing on?

[ian_luyt]

Thanks for the questions. I'm using a 30D, mostly in "P" mode. I have checked the focus lockup (this is a good suggestion and has been an oversight in the past). Subjects being shot consist mostly of people in public situations. I am often trying to focus on, for example, an individual but often pick up the focus on something just to the side of the person.

 

Good suggestions so far from all of you, thanks for the help !

[hjoseph7]

"I am often trying to focus on, for example, an individual but often pick up the focus on something just to the side of the person."

 

I would send it back to Canon, or get use to using the focusing points. Focusing points are very important especially in portraiture. That's why I often find myself putting the lens in Manual mode rather than AF, because it's allot quiker.

 

In any case, it seems that the 30D has a lot of horror stories to tell. Mine has worked especially well ever since I got it. Sorry but yours might just be a lemon. Dish it before the warranty runs out is my advice.

[keith_lubow]

It sounds like you have all the AF points activated, and the camera is choosing which one to use.

 

It will give you much better control to select a single AF point.

 

AF simply motorizes the operation of turning the focusing collar. It doesn't do the thinking for you. You still have to tell the camera what to focus on for decent results. Otherwise, the camera just chooses the point that has the most contrast.

 

So, my suggestion is to set the camera on one-shot AF mode, activate a single AF point, put it directly over what you want to shoot, focus, keep your finger on the focus button (either shutter halfway or * button, depending on how your camera is set up), and then compose the shot.

 

I think most people will be better served by putting control of AF onto the AE lock (*) button. Only occasionally will I put it back on the shutter usually on the occasions when I use AI servo focus (basketball action, for instance).

 

The more you leave to automation, the more you have to pay attention, actually...just to make sure the darned thing is doing what you want it to do!

 

Keith