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Thread: F3.5 - 5.5 What does this means?

  1. #1

    Default F3.5 - 5.5 What does this means?

    I know that the max aperture is F3.5 but why the range?? can someone clarify my doubts.
    Canon 450D/ F1.8 50MM/ EF-S 55- 250MM/ IS 18 - 15 MM

  2. #2
    Member lamergod's Avatar
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    Default Re: F3.5 - 5.5 What does this means?

    When you zoom,the aperture get's higher as you zoom to the most tele end of the lens.So example a 18-55 lens,at `18mm it will be at f3.5 while at 55mm it will be at f5.6

  3. #3

    Default Re: F3.5 - 5.5 What does this means?

    Quote Originally Posted by hyori View Post
    I know that the max aperture is F3.5 but why the range?? can someone clarify my doubts.
    example:

    nikkor 18-70 f3.5-4.5

    it's mean when it is 18mm, maximum aperture will be f3.5,
    when it's reach 70mm, maximum aperture will be only 4.5. it cannot get f3.5 in 70mm

  4. #4

    Default Re: F3.5 - 5.5 What does this means?

    It's called variable aperture. It lists the maximum aperture at the wide angle, and also at the maximum tele.

    FYI, if you google "F3.5 - 5.5 What does this mean" you get:
    http://wiki.answers.com/Q/What_is_th..._ed-if_af-s_dx
    Alpha

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    Default Re: F3.5 - 5.5 What does this means?

    Quote Originally Posted by hyori View Post
    I know that the max aperture is F3.5 but why the range?? can someone clarify my doubts.

    You still havent read up on the manual or other photography notes?

    The maximum aperture is f3.5 at the smallest focal length... But when you zoom in to the max, the maximum aperture becomes f5.5...

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    Senior Member zac08's Avatar
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    Default Re: F3.5 - 5.5 What does this means?

    Quote Originally Posted by hyori View Post
    I know that the max aperture is F3.5 but why the range?? can someone clarify my doubts.
    Very simple. This lens has a fixed diameter over a focal range. And aperture is based on the lens diameter to the focal length. Thus at the wider focal length, the aperture is f3.5 ratio based on the aperture diameter to the lens focal length. And NOW when you zoom in, the aperture size is still the same but the ratio to the focal length has changed and now gives you a aperture of f5.5 instead.

    Those higher end lenses with fixed aperture has a varying aperture size which adjusts itself to give a constant aperture ratio even at the longer focal lengths, and this is more difficult and more expensive.
    Michael Lim
    My Flickr Site

  7. #7

    Default Re: F3.5 - 5.5 What does this means?

    i see thanks! i understand now
    Canon 450D/ F1.8 50MM/ EF-S 55- 250MM/ IS 18 - 15 MM

  8. #8
    Deregistered shaoken's Avatar
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    Default Re: F3.5 - 5.5 What does this means?

    It's a variable minimum aperture.
    The minimum aperture changes over different focal length.

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