AI Servo Focussing Question

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Rodintee

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Russ
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Just been thinking about focussing in AI servo mode (assuming you are a Canonian).

As the sequence seems to me;

1. Lens is at max aperture tracking the target whilst shutter button 1/2 pressed.

2. Fully depress shutter button, aperture closes and shot is taken at the current focus setting.

3. Aperture then open back to max to retain focus track.

My question is, if you are in "machine gun" mode tracking a fast object does the aperture open and close for each exposure to keep the focus tracking as accurate as possible.

If so, can really fast shooting (10 FPS) in a 1DMk3 actually shoot faster than the lens can open/close the aperture.

Are aperture times published anywhere for lenses?

Just my thought for the day :)

Russ
 
Don't know about 10 frames a second but with my 8.3 (1DII) it stops down and opens between frames (and I can see through the viewfinder to keep the panning aligned)
 
Wow, I'm kind of surprised it can operate that quickly but there you go !!!

Wonder if some lenses can be outstripped by the body frame rate.
 
The shutter won't fire until the lens reports back that the aperture is stopped down. The frame rate published is a maximum and not always achieved....shooting at f/32 on an f/1.4 lens is likely to limit the frame rate somewhat as the aperture drive needs more time to achieve the correct position for each frame.

Bob
 
Have a look at this link. 0.04 sec for shutter lag for a 1D MkIIn isn't slow, I assume the 1D MkIII has something very similar. It also explains autofocus lag, shutter release lag etc, although it would probably depend on the glass you have on the camera as well and the light conditions.

http://www.impulseadventure.com/photo/shutter-lag.html
 
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