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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 05 Aug 2008 (Tuesday) 14:39
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AI servo/AI focus

 
shutter_blitz
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308 posts
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Aug 05, 2008 14:39 |  #1

I will shooting a fire spinning show tonight. I am planning on using AI servo, as the spinners are constantly moving and dancing. Or should I just let the camera do it with AI focus?
The venue is open air, dark. The spinners will mainly be lit by the fire, which is bright enough to lock focus and provide contrast.
If I set AF mode to AI focus and the camera kicks in AI servo once the object starts moving, after the shot is taken, is the AF mode reset to AI focus?


Gear:
Canon 50D
EF 50mm f1.4 USM, EF 70-200mm f/2.8 L IS USM
Sunpak 383
Quantaray QSX-9500

  
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poloman
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Aug 05, 2008 17:05 |  #2

Use AI Servo.


"All those who believe in psychokinesis, raise my right hand!" Steven Wright

  
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Vacation
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Aug 05, 2008 17:07 |  #3

I don't know the correct answer but I would go with AI Servio...I don't understand why anyone wouldn't want the focus to follow the subject in case it moves.

If someone knows the answer please let me know.


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Gatorboy
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Aug 05, 2008 17:26 |  #4

AI Focus sucks -- go with AI Servo.


Dave Hoffmann

  
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tim
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Aug 05, 2008 17:44 |  #5

AI servo is for objects that are moving at a constant speed relative to the camera. Use one shot. I've photographed fire jugglers a few times before, always on one shot, it worked fine. Focus and shoot quickly before they move too much.


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chrishunt
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Aug 05, 2008 18:08 |  #6

I agree with Tim. AI servo doesn't work well in poor lighting, and it does even worse when the subject is moving sporadically.

I'd use single shot with the center focus point only. Focus before every shot.




  
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poloman
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Aug 05, 2008 20:09 |  #7

Learned something here. Thanks Tim.


"All those who believe in psychokinesis, raise my right hand!" Steven Wright

  
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rral22
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Aug 05, 2008 20:20 as a reply to  @ poloman's post |  #8

I would think seriously of manual focus in really dim light. I would figure out an aperture that would give me just enough depth of field and then experiment with manual focus.

If the subject movement is not very "deep" you will likely find you have to make very small adjustments, and will be more accurate yourself. Sometimes in "dark" environments, if the camera loses focus, it may search badly for a few seconds. You are smarter than that, and will likely get even more keepers.




  
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shutter_blitz
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Aug 06, 2008 09:44 |  #9

Thanks, all. I used one-shot AF, lens was set to AF. Results were pretty good, although had to use slow shutter and so a lot of blurring can be see.


Gear:
Canon 50D
EF 50mm f1.4 USM, EF 70-200mm f/2.8 L IS USM
Sunpak 383
Quantaray QSX-9500

  
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AI servo/AI focus
FORUMS Photography Talk by Genre General Photography Talk 
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