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A “note” on the AF of this lens with a 7D:
I just received my copy late yesterday, and only had time for initial set-up, and basic tests such as Front/Back AF, etc.
When I test for Front/Back AF, I line-up on a “typical” 45 deg. “target”, focus manually, then turn the focus ring CCW to front focus slightly---take a few shots--- then, turn the focus ring CW until it's back-focused slightly & take a few.
I found that when the lens was “slightly” front focused it would repeatedly “snap” into focus—BUT--, when it was back-focused to the same degree it would/could not squire AF at all, even when I manually adjusted it closer to the correct position.
This was with C.Fn iii-4 set to (1)/ Focus Search=Off; which I had selected to keep my 100-400L from hunting in “grossly” out of focus situation.
When I changed the setting to Focus Search= ON, the Tamron was able to achieve AF from both directions however, when coming from a FF position it “snapped into focus—BUT--, when coming from a BF position it had to “hunt”/“cycle” to find it. The position of the Focus Limiter made NO difference.
The above behavior was both in One-Shot and IA-Servo.
I never experienced this anomaly with the 100-400L, or Sigma 120-300 OS even with a 2X TC attached, and C.Fn iii-4 set to (1) Focus Search= Off.
So, with my copy of this lens, there's an apparent problem squiring AF from a Back-Focused position.
Weather that's inherent in the design, or a malfunction, I'm not sure, but it didn't happen with the Canon or Sigma lenses, so it's not likely a 7D “problem.
I'll be taking it out today for some field shots, including some IA-servo BIFs .
Leigh
www.leighwax.com
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