Focus speed of 300 mm L 2.8 with 2x extender ?

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I'm considering the purchase of a 300 mm 2.8 + 2x extender to give me a 600 f5.6 . I have read this combo is slow to focus . My question is is it still fast enough to use as a wild life lens on my Elan IIe in the AI servo mode and still get good results ? Is it fast enough to track flying birds? Any help on this is greatly appreciated so I don't make the wrong buy . Thanks , D.C.

-- D.C. (dmconnell@charter.net), July 17, 2001

Answers

"Slow" is a relative term. "Slower than without the extender"- yes. "Slower than a zoom lens with(or without?) the extender"- no. USM/ HSM/ older motors play some role here, but the primes still AF significantly faster than zooms, and you should be fine.

-- Mike Greene (mgreene31@hotmail.com), July 18, 2001.

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