jerrykur wrote: Gust wrote:
Nathan, I think you-re right, but..
when my cam on a tripod, testing on a contrast static object, AI shooting, the AF is very chattering, not steady on the point.
its like te AF is constantly changing and searching
Isn\'t that how AI is supposed to work? If you leave your finger on the button you are asking it to constant recheck focus. With a stationary target that mean go off focus- recompute focus - set focus to new setting (which could be the same).
No, when IS is turned OFF and you are on a tripod with AI Servo AF enabled there should be zero hunting (after initial acquisition) if you keep the shutter button depressed; note, this is true only if both the lens and camera body don\'t have hardware issues.
One of my friends shoots college sports professionally; he experienced a total melt down during a football game using his 300 f/2.8 and 1DmkIIN. He brought the gear over to my house for testing and it turned out that while on a tripod static focus was perfect with either One Shot AF or AI Servo AF enabled. However, and this was really interesting, even though static focus (on a tripod) in AI Servo AF mode was perfect (as confirmed by my AF test fixture) something was vibrating and the resultant focus target picture had a very slight (not bad, just slight) smear, like a cloudy look to it (i.e. radial motion blur ... something was moving ... just a teeny tiny slight amount).
Anyway, outdoors with AI Servo AF mode enabled and while I was shooting a moving target (my buddy\'s car) the focus tracking error was in in the neighborhood of twenty (or more, who knows) feet; this confirmed his meltdown. The 300 f/2.8 was confirmed to be okay using my 1DmkII and the same moving car. After an overnight trip to Canon CPS found the issue with his 1DmkIIN body. It must have been a trivial fix because my buddy had the 1DmkIIN body on his doorstep in two days and it worked perfectly once again.
What I found interesting about my friends 1DmkIIN issue was that you can have perfect acquisition in either One Shot or AI Servo AF modes and it means absolutely nothing in when in comes to tracking error in AI Servo AF mode (i.e. static AF error can be perfect but dynamic can be absolutely next-county horrible ... go figure).
Regards,
Joe Kurkjian
Feb 06, 2010 at 10:38 AM
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