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Thread: burst rate decreases during AI Servo focus mode?

  1. #1

    Default burst rate decreases during AI Servo focus mode?

    is it normal for my 20d to experience a decrease in the burst rate when the focus mode is set to AI Servo? thanks

  2. #2
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    Default Re: burst rate decreases during AI Servo focus mode?

    i don't think so...unless the shutter is slower than 1/3 of a second...
    5D | 24-70L | 28mm f/1.8 | 580EX

  3. #3
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    Default Re: burst rate decreases during AI Servo focus mode?

    Quote Originally Posted by dan_1337 View Post
    i don't think so...unless the shutter is slower than 1/3 of a second...
    1/3s x 5FPS = 1.5s... its already much slower than the 5FPS that the 20D support... and do note that that doesn't include the blackout time... etc and continuous focusing as well.

  4. #4
    vince123123
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    Default Re: burst rate decreases during AI Servo focus mode?

    Wouldn't it naturally be slower if the camera is continually focussing?

  5. #5

    Default Re: burst rate decreases during AI Servo focus mode?

    when i used AI Servo to focus on a stationary structure and compared with the normal one shot focus, the latter had a higher burst rate quite close to 5fps while the former had a burst rate of only about 2fps. shutter speed used in both instances were faster than 1/500s so i dun think shutter speed is a concern here.
    Last edited by aloyteo; 21st January 2007 at 09:01 PM.

  6. #6
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    Default Re: burst rate decreases during AI Servo focus mode?

    Quote Originally Posted by aloyteo View Post
    when i used AI Servo to focus on a stationary structure and compared with the normal one shot focus, the latter had a higher burst rate quite close to 5fps while the former had a burst rate of only about 2fps. shutter speed used in both instances were faster than 1/500s so i dun think shutter speed is a concern here.
    most probably is that after the mirror have come down, the camera will try to confirm focus before taking another shot... making it to slow down...
    im not very sure as well, but this could be one of the reason behind.

  7. #7

    Default Re: burst rate decreases during AI Servo focus mode?

    Quote Originally Posted by ExplorerZ View Post
    most probably is that after the mirror have come down, the camera will try to confirm focus before taking another shot... making it to slow down...
    im not very sure as well, but this could be one of the reason behind.

    i not sure also but what i know is that even in AI Servo Mode the burst rate should still be around 5fps. any other 20D users can confirm? thanks

  8. #8

    Default Re: burst rate decreases during AI Servo focus mode?

    When you use single shot focus... once the cam achieve AF lock, the shutter will release and continue until you let go the shutter button... it will not care if the subject moves out of focus in between frames.

    When you use AI focus, once the cam achieve AF lock, the shutter will release and continue until you let go the shutter button. However the cam will re-confirm the focus and subject's vector after every frame. You can still achieve 5fps if your subject is either stationary or constantly moving.

    When you use AI servo. First shot will fire regardless AF lock or not, subsequent shots AF must lock on before shutter can release.

    So in your situation, it could be that the AF cannot be lock on subject.

  9. #9
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    Default Re: burst rate decreases during AI Servo focus mode?

    Quote Originally Posted by ExplorerZ View Post
    1/3s x 5FPS = 1.5s... its already much slower than the 5FPS that the 20D support... and do note that that doesn't include the blackout time... etc and continuous focusing as well.
    oops, my bad. for some reason i thought it was 3fps. got the 350/400D mixed up with the 20D.
    5D | 24-70L | 28mm f/1.8 | 580EX

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