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Thread: what do the terms on my lens mean?

  1. #1

    Default what do the terms on my lens mean?

    7.1-21.3mm
    1:2.8 - 4.9

    The above measurements are printed on my digicam lens.
    Other than saying the cam has 3X optical zoom, i donno what's the significance of the rest. (ie. what do they mean exactly???)
    Can someone kindly explain to me? Thanks in advance.

  2. #2
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    Default

    7.1-21.3mm = focal length
    1:2.8 - 4.9 = aperture

  3. #3

    Default

    Or more specifically, your "7.1-21.3mm" means the focal length the lens can zoom. Taken on it's own, it's probably of no useful meaning except that it tells you it has a OPTICAL zoom ratio of 3x (21.3/7.1 = 3).

    The "1:2.8-4.9" means that the lens, at 7.1mm focal length has an aperture of f/2.8, and at the longest 21.3mm focal length has an aperture of f/4.9. The aperture affects the amount of light received by the sensor, among other things. Technically speaking, the smaller the f-number the more light it can collect and can shoot better in low-light situations.

  4. #4

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    Thanks for the clarification. Can the 7.1-21.3mm be interpreted in any way to give other info, like optimal distance between cam & subject (what-do-u-call-this) etc?

    I'm thinking of getting an add-on macro filter for my cam (want to improve my macro shots)... what range of "measurements" shd i be looking at for the filter? (Hope this isnt a dumb question!)
    Last edited by isis; 18th May 2004 at 12:51 AM.

  5. #5

    Default

    Quote Originally Posted by Ah Pao
    The "1:2.8-4.9" means that the lens, at 7.1mm focal length has an aperture of f/2.8, and at the longest 21.3mm focal length has an aperture of f/4.9.
    those are maximum apertures you are talking about

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