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| p.1 #5 · Question about 1D Mark IIN AI Servo AF |
Ok, so from what you're saying is due to the lens being "low-contrast" (since the lenses are always wide open before the shot is taken to allow light hit the AF sensor), it confuses the 1D body to do this chattering (due to its high-speed prediction algorithm vs. the lower-end AF modules) and become overly re-active in AI-servo mode.
I'll have to dig up a 70-200 2.8 and a slower speed lens to test the above soon. But it sounds very interesting (especially coming from Nikon's AF).
I did notice when I had borrowed the 70-200mm II IS (stablizer off) attached to this 1D IIN body, that the AF is far quicker to initially lock focus vs. my D700 with the 80-200mm AF-S. The fine focus mechanics on the 70-200mm II IS is far shorter than the 80-200mm AF-S (as much as 1.5" more of turn mechanically from infinity to MFD). But the tracking method is far more stable on the D700 vs. the 1D IIN: hence the erratic/quick refocus of the Canon's AI Servo AF. I love the focusing speed, but not this overly erratic focus method too much (this was evident with all 3 bodies I had).
Also, when focusing from a near to close subject (such as focusing a quarterback then onto a receiver), the Canon is quicker at acquiring focus. Tracking is same with both system (with the Canon being more erratic).