1D Servo AF prediction behavior - expert advice sought

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fishy wishy
fishy wishy Veteran Member • Posts: 8,479
1D Servo AF prediction behavior - expert advice sought

I have seen strange AF performance on 1D II & 1D III with Sigma lenses 70-200 II & 50-150 II, probably released just after the 1D III. Both are HSM, equivalent to the USM type.

Both lenses on both cameras do fine in single shot AF, and even in Servo if the subject is not moving, or if I'm not waving the camera about.

If the subject is moving or I am waving the camera too much, I have noticed how the AF pulls to front-focus in a burst. The first shot is in focus and then focus shifts to the front in a burst of frames. It's quite regular and predictable if the stated condition is met. As far as I can tell it's always to the front, which across two lenses and two bodies makes me think it's deliberately programmed as some kind of second-guess autofocusing to expect the subject is coming towards the camera.

Has anybody else noticed this behaviour with any lenses on the 1D series? Strangely the lenses didn't provoke the same behavior out of 20D, 30D, 40D, 50D. At the time of their release or now.

I am about to do a test on this with different manufacturers to see if it's peculiar to Sigmas or if Canon lenses behave any better.

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Canon EOS 20D Canon EOS 30D Canon EOS 40D Canon EOS 50D Canon EOS-1D Canon EOS-1D Mark II Canon EOS-1D Mark III
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