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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 23 Oct 2006 (Monday) 12:50
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20D re-focuses when re-composing

 
Ian ­ Trott
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Joined May 2006
     
Oct 23, 2006 12:50 |  #1

Wondering if any Canon DSLR users out there in Cyberspace have run into this peculiar problem. Seems to happen after the camera has been in use off and on for a few hours - wedding photography. Anyway, what happens is ... I'm strictly using the center focus point, focus on my subject, shutter release depressed halfway, then I recompose the shot. Shutter release still being held halfway - no change in pressure being applied, and when I depress the shutter release all the way down there is a VERY noticable lag before the shutter activates and when it does the center focus point re-focuses on wherever it's now aimed a split second before shutter activation. All this after recomposing my shot. Now my subject is of course out of focus. This problem will almost certainly have to be investigated and repaired by Canon, but I'm trying to find out if anyone has ever had a similar problem and what the outcome was.
Thanks to all who respond.
Ps ... in all cases I've had a 550 EX flash attached but not necessarily turned on.




  
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AirBrontosaurus
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Oct 23, 2006 12:54 |  #2

I'm pretty sure that's how it's supposed to work. If you have it in AI-Focus mode, the camera is supposed to try and predict the movement of its subject. That way, if you focus on something, and while you still have the shutter held down it moves (to a large degree, anyways), then the camera re-focuses so you don't miss your shot.

To fix this, I would first change it to one-shot AF mode. If that doesn't work, try using manual focus. Have the camera focus on what you want, and then switch it into manual mode. That way, it won't ever refocus because it can't.


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Tee ­ Why
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Oct 23, 2006 12:57 |  #3

Yup, AI focus will do that everytime, so will Servo.
Use custom function 4-1 and you don't have to worry about that.
If you are in One shot, then it's something else.


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cfcRebel
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Oct 23, 2006 13:05 |  #4

As Tee Why said, use CFn4-1 to separate the autofocus from the shutter button. It allows you to use the * button to AF, then use the shutter button to meter.


Fee

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Ian ­ Trott
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Oct 23, 2006 14:30 as a reply to  @ cfcRebel's post |  #5

Sorry folks, forgot to mention one important point. I'm shooting in "one shot mode" (evaluative metering) with CF4 set to default "0". I just now tried setting CF4 to lock focus with the * button and lock exposure with the shutter release - can't remember which number that is. It works, but only some of the time, and just as often the shutter won't lock the exposure. That suggests my problem is with the shutter mechanism - at least to my way of thinking .... which isn't always the brightest.
Again, thanks in advance for any al all tips/suggestions.




  
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badrotation
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Oct 23, 2006 18:00 |  #6

Dirt in the shutter button.... Ran in to this problem with all my bodies... Easily fixed if you want to disect the camera, or just send it into canon.




  
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braduardo
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Oct 23, 2006 18:09 |  #7

I had dirt in my * button... Eventually I just decided to use a razor knife to pop the button out... Cleaned it up.. but had to use a drop of super glue to hold it back in place... Not a lot, just enough to keep it stuck to the button inside. Works like a charm now. I wouldn't do it if I had a better camera that would be worth the repair bill, but to spend $100-200 to fix a camera that goes for $300 give or take, I would rather just do the simple fixes myself.


:rolleyes: ----Brad---- :rolleyes:
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40D: EF 17-40 f4 L ---- EF 70-200mm f4 L ---- EF 50mm f1.4 ---- EF 85mm f1.8

  
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20D re-focuses when re-composing
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