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Thread: IF - Internal Focusing....???

  1. #1

    Default IF - Internal Focusing....???

    Hi all,

    I am rather puzzled by my Tamron SP AF17-50mm F/2.8 XR Di II LD Aspherical [IF].

    Isn't IF means internal focusing, where is does not change the physical length of the lens?

    Why is it that when I zoom the lens, it extended the physical length of the lens?

    Or does it means that it doesn't change the length when focusing? I blur liao.... any sifu can help enlighten me?
    Last edited by kevyan; 16th April 2008 at 03:13 PM.

  2. #2

    Default Re: IF - Internal Focusing....???

    Quote Originally Posted by kevyan View Post
    Hi all,

    I am rather puzzled by my Tamron SP AF17-50mm F/2.8 XR Di II LD Aspherical [IF].

    Isn't IF means internal focusing, where is does not change the physical length of the lens?

    Why is it that when I zoom the lens, it extended the physical length of the lens?

    Or does it means that it doesn't change the length when focusing? I blur liao.... any sifu can help enlighten me?
    Zoom is different from focus.
    Alpha

  3. #3

    Default Re: IF - Internal Focusing....???

    internal focussing refers to the length of the lens doesnt change during focusing. some of the newer lens extend when it is focusing. when u are zooming in, its zoom, not focusing.

  4. #4

    Default Re: IF - Internal Focusing....???

    Ah... okay.... I koo koo.... not sure, so I ask all the sifu here.... so paiseh....

    Thank you very much.

    Quote Originally Posted by flipfreak View Post
    internal focussing refers to the length of the lens doesnt change during focusing. some of the newer lens extend when it is focusing. when u are zooming in, its zoom, not focusing.

  5. #5

    Default Re: IF - Internal Focusing....???

    Quote Originally Posted by kevyan View Post
    Hi all,

    I am rather puzzled by my Tamron SP AF17-50mm F/2.8 XR Di II LD Aspherical [IF].

    Isn't IF means internal focusing, where is does not change the physical length of the lens?
    ....
    Or does it means that it doesn't change the length when focusing? I blur liao.... any sifu can help enlighten me?
    "it means that it doesn't change the length when focusing"

    -> you actually just answered your question. =)
    D80|Tamron 17-50mm f/2.8|Nikon 50mm f/1.8D|80-200mm f/2.8D
    PortFolio | Photo Blog

  6. #6

    Default Re: IF - Internal Focusing....???



    Quote Originally Posted by senray View Post
    "it means that it doesn't change the length when focusing"

    -> you actually just answered your question. =)

  7. #7

    Default Re: IF - Internal Focusing....???

    Quote Originally Posted by kevyan View Post
    Ah... okay.... I koo koo.... not sure, so I ask all the sifu here.... so paiseh....

    Thank you very much.
    its ok. everyone's new at 1 pt or another.

  8. #8

    Default Re: IF - Internal Focusing....???

    no lah! not to embarass you or anything, I don't even know what all those terms like "IF", "AF" last time too. Once you get the hang of it, it is as easy as ABC.

    Don't we all? =)
    D80|Tamron 17-50mm f/2.8|Nikon 50mm f/1.8D|80-200mm f/2.8D
    PortFolio | Photo Blog

  9. #9
    Senior Member giantcanopy's Avatar
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    Default Re: IF - Internal Focusing....???

    Internal Focusing. A conventional double helicoid focusing system requires that all lens groups be moved by the lens barrel to either the front or rear during focusing. This mechanism is not only complicated but bulky, more so in the case of telephoto lenses where the extra physical length of the lens requires the use of a heavier gauge metal with a consequent increase in size and weight. In addition, a change in the length of the lens when focusing results in unbalanced hand held shooting.

    To remedy this situation, Nikon developed the Internal Focusing (IF) system. With IF, only the internal small lens group shifts during focusing with no change in the lens' physical length, permitting more compact, lightweight construction and a closer minimum focusing distance for telephoto lenses. Additional benefits include faster focusing and a reduced diameter of the focusing ring due to a simplified focusing mechanism.


    From the encyclopedic mir website link

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