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Old Oct 26, 2003, 6:56 PM   #1
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Default How to choose which zone to focus in AiAF (A70)?

I'm a bit confused by AiAF. I know that with A70 while focusing it selects from 5 zones. With shutter button half pressed sometimes it'll show one off-center frame, sometimes 2-3. That, I understand, what camera thinks I want to focus on. But how do I choose which frame to use? A70 can't focus on 2 separate plains, can it? Is there a mechanism to choose a particular frame?

Or in case of a single off-center frame, what if I actually want to focus on the center subject? Focus lock won't help if AiAF frame is substantially closer or far away than the subject I have in mind. Certainly there's always center frame focus mode but then how Canon meant to use AiAF?

Thanks!

PS. A70 user manual wasn't of any help here.
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Old Oct 26, 2003, 10:32 PM   #2
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I guess I found the answer though not sure I like it . High-end Powershots such as S45/50 and G-series have something called FlexiZone AF/AE that works with AiAF and allows to select a zone or even move it. A-series seem to lack this functionality. Here's a quote from Canon's site:
Quote:
The PowerShot S50 and S45's 9-point AiAF lets you focus your subject no matter where it appears in the viewfinder.

For more freedom, FlexiZone AF/AE let you select which part of the frame you wish to focus on without moving your camera. Flexzone AF is available in the P, Tv, Av and M Shooting Modes.
The "dumb" AiAF on A70 basically renders it pointless in most cases. No wonder I was getting so many out of focus photos. Perhaps uncontrollable AiAF has its usage for candid or fast action shots when there's no time to properly compose and focus or fot totally novice people who don't know what focus is. In all those cases ther's at least some guarantee that few shots may come focused right.

Otherwise AiAF seems to be a worthless and even negative gimmick for most ordianry shooting situations. Canon shouldn't have made it the default.
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Old Oct 27, 2003, 4:40 AM   #3
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Default A70 focus

What I did, and I think a lot of other A70 owners, was turn of the AIAF and just use the "standard" way of focussing in the middle. If I want to focus on something that is not in the middle I use focus lock.
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Old Oct 29, 2003, 2:31 AM   #4
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If I don't like AiAF's focusing zone suggestion but don't want to turn it off, I just move the camera slightly sideways, halfpressing the shutter button, until the rectangular appears where I want it. Then I use focus lock, recompose the scene and make a shot. But usually AiAF works just fine, and I have no need to correct it.
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Old Oct 29, 2003, 2:54 AM   #5
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When AiAF suggests more than one zone, I believe it means they all will be in focus, you don't need to choose between them. The camera can't focus on two separate plains obviously. If the objects suggested for focusing are located at different distances from the camera, I believe it just means that they are still within the same depth of focus.
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Old Oct 29, 2003, 11:08 AM   #6
ir
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I have an A70, and I turned my AiAF off on the first day and have never turned it back on. Center focus is fine. If you want to focus on something off center, just put it in the center press the shutter button half way for a focus lock, then re-compose the frame how you want it. I use a 35mm Canon SLR and do the same thing.

Sometimes it could be a problem if you're using spot or even center weighted metering because the exposure might change as you move the center of the camera to an area of different lighting, since the half press also locks the exposure. But that's photography. I actually use this to take some quick exposure bracketing shots sometimes. Instead of going manual, just get light metering from different parts of the frame (making sure you have something in the proper plane to focus on - not usually a problem for landscape type shots).

I agree that the AiAF as implemented on the A70 is probably more suited for novices. I found it would latch onto whatever was closest most of the time- like the tree branch and not the human subject in back that it was supposed to be framing.

ir
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