Maintian Focus w/ Moving Objects.... AI-Servo maybe?

Discussion in 'Beyond the Basics' started by keith204, Jun 15, 2007.

  1. keith204

    keith204 No longer a newbie, moving up!

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    There was a similar topic regarding AI-Servo, but going in another direction. My question is: What are the pros & cons of using AI Servo? I take dirt track photography, and often I am taking multiple pictures of a car coming spinning towards me. In this case, is AI Servo a good thing? Also, what about the dust the car makes--will it throw off the AI Servo and cause my focusing to go nuts?

    Basically
    1) Is AI Servo the best for my needs?
    2) Does anyone have any tips, based on my circumstances?

    Rebel XT
    18-55
    Canon 50mm 1.8
    Sigma 70-200 f/2.8
    Canon 430EX
     
  2. Garbz

    Garbz No longer a newbie, moving up!

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    It depends. Can you camera focus in the milliseconds between each shot? AI-Servo is good for tracking moving objects but my own experiments and it seems the opinion of quite a few pros in the area is to manually focus on a spot where the car will come through and then shoot when it reaches that point.

    I find moving the camera quickly sometimes throws off the focus despite the predicative focus tracking in my camera
     
  3. bakuretsu

    bakuretsu TPF Noob!

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    AI Servo is touch and go I think. There are times when it seems to help, and I think the manual says it's best suited for things that are mostly traveling toward or away from you, which I suppose the cars would be.

    That said, what Garbz suggests sounds like a good idea to me. Manually focus to a certain spot you are pretty sure the car will pass through, set your camera on continuous drive, and just hold the button as they drive through it.

    Sports and action photography like that is seldom a situation where you can press the button once and get exactly what you wanted; it's too erratic to predict the exact millisecond when things will be perfect and even human reflexes are inadequate for some events.


    That's my $0.02.
     
  4. BoblyBill

    BoblyBill TPF Noob!

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    I don't think there is anything to add to this one. Great advice guys.
     

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