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Thread: Focal Length

  1. #1

    Join Date
    Sep 2010
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    julius

    Focal Length

    How do I set the focal length. I have a canon 100d with a canon zoom lens ef-s 55-250mm 1:4-5.6 is

    help please

  2. #2
    David's Avatar
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    Apr 2008
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    David

    Re: Focal Length

    Julius - The straight answer is that you have a zoom lens with a variable focal length of between 55 and 250 mm. To set it at any value between those limits turn the knurled sleeve on the lens. Usually, such a lens is used for compositional reasons so as to bring more or less of a scene into the frame - hence turning the sleeve to achieve this.

    It may be that this is not exactly what you meant - so please come back to us.

    David

  3. #3
    rpcrowe's Avatar
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    Richard

    Re: Focal Length

    If you mean "How do I preset the focal length?" Turning the knurled knob will match up the numbers "55; 70; 100; 135; and 200" with the white indicator mark. This is your approximate focal length. For focal lengths in between these numbers the photographer must "guestimate".

    By the way, I said "approximate focal length" because these markings, and the focal length of a zoom lens as a whole. are only accurate when the lens is focused at infinity.

    BTW: I seldom look at the focal length I have chosen exept through the viewfinder.

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