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Old Jan 28, 2005, 8:49 PM   #1
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Quick background. I used the 10D for a year and a quarter. I liked it.

But a good offer on my 10D and the better focus on the 20D seduced me.

So I spend several hours shooting owls today. Did well. But I had a problem. I believe something is wrong with the focus tracking of the 20D.

If I tracked the bird in flight with the sky in the background it worked as expected - it consistently followed it (or tried) and never skipped to the background. But the instant the bird flew down so the background was something else (buildings, green trees, snow, brown/dead grass) it shifted focus to the background. Consistently, every time. If I followed the bird it tracked the background. If the bird flew up so the sky was behind it again, it locked back on the bird.

I never saw this behavior with the 10D. Ever.

This happened with center AF point or with all of them. Didn't matter.

And to spice things up, if I switched to one shot, it locked on just fine even when the background wasn't the sky.

Has anyone else had focus tracking problems with the 20D? Any tips? Seen any threads about this on other forums? I am really frustrated at this point. I almost frostbit my fingers and toes shooting today and I didn't get nearly as many good pictures because of that camera.

Eric

Ps. I was using the 600mm f4 with and without the 1.4TC. Didn't matter.
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Old Jan 29, 2005, 9:02 AM   #2
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Here is an example of what I was trying to photograph:
http://www.stevesforums.com/forums/v...85&forum_id=11

I believe this was done with ai-servo. I believe it worked because of the dark background, but soon thereafter it shifted to the background. (Maybe due to the dark wing being exposed?)

Eric
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Old Jan 29, 2005, 12:16 PM   #3
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Nice picture, Eric. Did you use AI Focus or AI Servo mode? The manual isn't terribly clear, though I have read some posts about problems with AI Focus, mostly with slowing down focus.

I haven't taken any shots of in-flight birds yet, pending getting a suitable lens. My bank account is still recovering from the 20D with 17-85IS and a new Dell for processing photos.

We have an amazing variety of raptors up here on Whidbey Island in Puget Sound. Besides two kinds of eagles, we have close to a dozen kinds of hawks as well as several owls. A mouse doesn't have a prayer .

Where near Boston? I graduated from High School in Wayland, a loooong time ago.
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Old Jan 29, 2005, 3:45 PM   #4
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That picture, actually, was done with AI Servo tracking (not the middle one, the bottom one.) I think AI Focus is dumb and should be removed. Let it pick when to lock focus and when to adjust it because of motion? No. I've never had that setting work, I just don't use it.

Sounds like you've got a great place for raptor photography. Lucky you. We're having a bad year.

I've lived in Waltham, Lexington, Bedford, and grew up in Lincoln.

Eric
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Old Jan 30, 2005, 11:06 PM   #5
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Hi Eric,

Nice shot. I am not a bird shooter but was shooting an eaglethe other day and had the same queries regarding the AF options. It seemed to me to make sense what was going on with the camera.

In AI Servo mode, when shooting against the sky (and say using the centre AF point only), if you get the bird centred then the camera will AF correctly, and change focus while the bird remains centered if the bird was to move. If the bird moves slightly off the centre AF pointwhile you shoot angainst against the sky, as there islittle contrast in the sky there isnothing for the camera to refocus on, so the focus doesn't change.However when the bird dips toa background suchas a mountain, when the bird moves off the centreAF point, the camera will refocus on the mountain which is now on the AF point.

I am not sure how this compares to the 10D behaviour or if my explanation is right but that is how I explained to myself.You can test this by pointing at the leaves of a tree and then the sky. The use of Ai Focus mode also confuses me a little and I haven'tused it.

PS Here is my shot pretty much untouched. I was only usingthe 70-200L with no IS and this was handheld so it is a long way from your great shot.

cheers, Tim
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Old Jan 31, 2005, 10:53 AM   #6
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:?Hi Eric, timmy glad you guys strted this thread as I was trying to come up with a similar question.

When you guys refer to center spot focus, are the other spots turned off? I have been expirementing with the AI focus mode and having diffuculty also. My problem is I have no experience to draw from. Now that you have brought this up, I will see what I can observe also.
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Old Jan 31, 2005, 11:27 AM   #7
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I have not tried tracking with AI Servo yet, I guess I don't look forward to doing so now.

Golfer: do you mean the real AI_focus mode and not AI_servo?

I think AI_focus is brain damaged. AI_focus is supposed to work asone shot mode unless it detects motion, then automatically switch to AI_servo. I find in this mode it will focus on a static subject then for no reason switch over to AI_servo and focus on something completely different as it decides a fencepost has suddenly startedmoving.

For myself I always pick a focus point manually, letting the camera pick one usually ends up with focus on something I do not want.

Peter.
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Old Jan 31, 2005, 12:32 PM   #8
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Golfer, yes we mean that we turn off all the other AF points except the center one. The reason for this is two fold. One, the center point is better than the others. And two, I don't want the camera suddenly thinking that the thing I want to focus on is under another AF point. If I pick the AF point, then I know exactly which one it will use. More control for me, with the added difficulty of not having the benefit of the other points when tracking.

TimmeyB, (& Golfer)
I agree with PeterP, don't use AI Servo. I've basically never had it work right. Like what PeterP said, I've had it switch to AI Focus for no reason that I saw. I wish they'd dump it and spend the engineering resources on something more useful.

Nice eagle shot, BTW. That is a rather young one... they are fun to watch and shoot, aren't they?

To all!
I just remembered something that I forgot before. I seem to recall that the AF points are smaller on the 20D than on the 10D. (On the 10D, it's actually larger than the center circle on the screen.) Maybe that is throwing me off. Maybe I'm not as good at tracking the bird? The thing that makes me lean away from this is that it did basically happens every single time. You'd think it would work some times and not others.

Eric
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Old Jan 31, 2005, 4:15 PM   #9
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Golfer wrote: "When you guys refer to center spot focus, are the other spots turned off"

That was how I was shooting. But now I think about it I wonder what the results would be with all AF point turned on. The camera should AF onthe closest object, which for birds would normally be the bird and the not the mountian in the background.

Maybe it would be easier to track the birdall AF points turned on then, and in AI Servo mode. Have you tried that Eric?

ToEric: Yes they are really fun to watch. Amazing creatures.







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Old Jan 31, 2005, 8:46 PM   #10
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Yes, I did try it with all AF points, and it still shifted to the background.

It has been suggested elsewhere that I contact canon support because they believe it should work better than it is for me. I'm seriously thinking of contacting them. The downside is... when do I not use the camera? There are always opportunities.

Eric
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