Diametre of Apertures?

Discussion in 'Photography Beginners' Forum' started by Harmony, Mar 22, 2009.

  1. Harmony

    Harmony TPF Noob!

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    Hey everyone!

    I was wondering if anyone knew the answer to my question, because I've searched high and low with no luck!

    What is the diametre of the following apertures in millimetres?

    f/2
    f/2.8
    f/4
    f/5.6
    f/8
    f/11
    f/16
    f/22

    Thanks in advance!
     
  2. Tolyk

    Tolyk TPF Noob!

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    It's relative to what focal length you're shooting at.
     
  3. Dwig

    Dwig TPF Noob!

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    They are exactly what they say they are.

    f/4, for example, means "focal length divided by four". The diameter of the aperture (this is not necessarily the diameter of the hole created by the iris, btw) of a 100mm lens set to f/4 is 25mm since f/4, where f=100, equals 100mm/4 or 25mm.
     
  4. Harmony

    Harmony TPF Noob!

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    Okay... so, for instance,

    50 mm lens: f/2 = 25 mm

    Thanks!
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Technically speaking, the F number is the ratio of the focal length and the entrance pupil...not necessarily the physical aperture.
     

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