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Thread: Lenses

  1. #1
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    Default Lenses

    Can someone explain something to me?

    For example, saw this lens on the Sigma website

    Sigma 135-400mm F4.5-5.6 DG

    What does the F4.5-5.6 mean? I know normally it is the maximum aperture, but i'm sure this does not mean the MINIMUM aperture is 5.6 right? Is there a way to see the MINIMUM aperture?

  2. #2
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    Default Re: Lenses

    Quote Originally Posted by hairygorillaz View Post
    Can someone explain something to me?

    For example, saw this lens on the Sigma website

    Sigma 135-400mm F4.5-5.6 DG

    What does the F4.5-5.6 mean? I know normally it is the maximum aperture, but i'm sure this does not mean the MINIMUM aperture is 5.6 right? Is there a way to see the MINIMUM aperture?
    "135-400mm f4.5-5.6" means that the maximum aperture is f4.5 at 135mm, and gradually reduces as you zoom further, down to a maximum aperture of f5.6 at 400mm. This is what's referred to as a "variable aperture zoom lens", as opposed to a "constant aperture zoom" or "fixed aperture zoom" (e.g. 70-200 f2.8 means the zoom has a maximum aperture of f2.8 throughout the entire zoom range). Variable aperture zooms are cheaper and lighter; constant aperture zooms are faster lenses and usually produce better image quality ('cos they're usually professional-quality lenses).

    The minimum aperture varies from lens to lens; in the case of the Sigma 135-400 f4.5-5.6, it's f32. The minimum aperture is usually found in the lens specifications, e.g.:
    http://www.sigmaphoto.com/lenses/len...75&navigator=3

    Hope this helps.
    "Photography is 50% photographer, 40% light, and 10% equipment." -- Petteri Sulonen

  3. #3
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    Default Re: Lenses

    do that means that the more i zoom in, the amount of light i can take in, with shutter speed and ISO constant, decreases? So in other words, the maximum amount of light i can take in drops?

  4. #4

    Default Re: Lenses

    That is correct. If you were to shoot say a white wall at 135mm at f/4.5 with the right exposure, then as you zoom in to 400mm with ISO and the shutter speed constant, you should have your white wall now underexposed by about 2/3 stop since 4-5.6 is one stop.
    5D MII w/16-35L,Sigma 28-70&Nikkors(35f2,85f1.4,105f2.5,180f2.8ED)

  5. #5
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    Default Re: Lenses

    ok. got it. Thanx for your help guys. :P

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