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Thread: What does "fast" mean?

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    Default What does "fast" mean?

    Sorry for sounding like a complete n00b, but when people refer to a lens as "fast", are they talking about wide aperture (so the shutter speed is faster) or faster AF response? Or is it sonething else?
    Thomas
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    Default Re: What does "fast" mean?

    Quote Originally Posted by srtgray View Post
    Sorry for sounding like a complete n00b, but when people refer to a lens as "fast", are they talking about wide aperture (so the shutter speed is faster) or faster AF response? Or is it sonething else?
    They mean that the maximum aperture is wide (low number), so that they can use a faster shutter speed in the same light.

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    Default Re: What does "fast" mean?

    Thanks!
    Thomas
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    Default Re: What does "fast" mean?

    Of course, the fast-ness of a lens is relative to its category. If we use the 35mm camera lenses as our guide, then we can categorize fast lens speed for the following effective focal length's as:

    20mm-21mm (
    Fast = F/2.8)
    24mm-28mm (F/2)
    35mm (F/2)
    50mm (F/1.4)
    75mm-105mm (F/1.8 - F/2)
    135mm-200mm (F/2.8)
    250mm-300mm (F/2.8)
    400mm (F/4)
    Last edited by jap; 10-14-2009 at 02:40 PM.
    Regards,
    J A P

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    Default Re: What does "fast" mean?

    So is a 4/3 200mm lens at f4 considered fast?
    Thomas
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    Default Re: What does "fast" mean?

    Quote Originally Posted by srtgray View Post
    So is a 4/3 200mm lens at f4 considered fast?

    According to the listing I provided, yes. Of course, that listing is based on equivalent focal length (efl) 400mm lens being considered fast at F/4. The 4/3's 50-200mm zoom (efl 100-400mm) is certainly considered fast at F/2.8-3.5.
    Regards,
    J A P

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    Default Re: What does "fast" mean?

    Coo, I'm learning lots here Thanks.
    Thomas
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    E-5+HLD-4x2; E-1+SHLD-2; 8mm FE; 7-14; 11-22; 14-35; 35-100; 135-400; EC-14; EX-25; FL-50Rx2

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