New Telephoto Lens Question...

This is a discussion on New Telephoto Lens Question... within the Digital Cameras, Lenses & Accessories forums, part of the PHOTO FORUM category; My Canon 70-300 IS USM just arrived and although I am quite excited to use it, the autofocus seems slower than I expected, especially at ...


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  1. #1
    Senior Member
    Join Date
    Jan 2008
    Posts
    256
    My Canon 70-300 IS USM just arrived and although I am quite excited to use it, the autofocus seems slower than I expected, especially at 300 mm. It moves quite fast when it is fine focusing, but is slow when going through an entire autofocus cycle.

    Is it just me? Or did I get a lemon?

    Maybe if I saw a video demo of the autofocus, I could tell if there is something wrong with it. If anyone knows of any I would appreciate it!
    Canon Rebel 400D/XTi, EF-S18-55mm, EF 70-300mm IS USM, EF-S 60mm f/2.8 Macro, EF-S 10-22mm, Speedlight 430EX II


  • #2

    Join Date
    Aug 2007
    Location
    Cambridge,UK
    Posts
    1,025
    PHOTO EDITING OK
    I remember reading reviews about this Monkey when I was thinking of one about a year ago.
    One of the plus points was its fast Autofocus!
    Got these details from Bob Atkins website;
    Autofocus Speed
    Just as Canon claimed, the new lens has faster autofocus. My tests showed an average time of 0.65 seconds to shift focus from 1.5m (closest focus) to infinity with the lens on an EOS 20D. The older 75-300 lens took an average of 0.9 seconds, so the new version is 33% faster.

    It's also quicker to "turn around", i.e. when focusing from infinity to closest focus, pausing, then reversing to focus from close focus to infinity. The new lens took around 1.65 seconds, the old lens took around 2.6 seconds. Not only is the focus faster, but the pause between reversing directions is shorter.

    Whole review is Here
    Bets to call in a local shop and compare with yours.

    HTH

    Peter
    Canon 40D, 30D, 70-200 L, 100 Macro, 75-300, 24-85 & 50 1.8

  • #3
    Photographer of sorts
    Join Date
    Feb 2008
    Location
    Hampshire, UK
    Posts
    732
    PHOTO EDITING NOT OK
    The Canon EF 70-300mm f/4-5.6 IS USM is not one of Canon's fastest focusing lenses.

    Canon has TWO types of "USM" focus motor; "ring-USM" which is very quick, silent and is fitted to (mainly) the top-end Canon lenses and "micro-USM" which is only a little better than a conventional micro-motor AF mechanism.

    The 70-30mm f/4-5.6 IS "USM" has the slower and less effective "micro-USM" system. Peter is indeed correct in that it is a better implementation than the 75-300mm "USM" (which was also "micro-USM") but it is still a long way short of most lenses fitted with the full ring-type USM.

    Without personally using your lens I couldn't really say whether it is performing correctly or not, but don't expect miracles with the 70-300/4-5.6 USM. It is never going to be blisteringly quick. It is normal for it to be slower to focus at 300mm as lens AF speed is to a large part dependant on maximum aperture and it is a full stop slower at 300mm than it is at 70mm.


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