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Thread: Focal Length Question.

  1. #1

    Default Focal Length Question.

    Hi guys,

    I have been asked by many people what does the 'mm' in the focal length means. I was stumped. Din know how to reply. Anyone able to help me out?

    i.e.
    17mm is wide angle.
    200mm is telephoto.

    what does 17mm means? like why term it in 'mm' ? how do they get the 'mm' ?

  2. #2
    Senior Member
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    Default Re: Focal Length Question.

    Quote Originally Posted by ShiNn View Post
    Hi guys,

    I have been asked by many people what does the 'mm' in the focal length means. I was stumped. Din know how to reply. Anyone able to help me out?

    i.e.
    17mm is wide angle.
    200mm is telephoto.

    what does 17mm means? like why term it in 'mm' ? how do they get the 'mm' ?
    mm as in millimeters, for example 1 cm = 10mm
    Home is where the heart is.

  3. #3

    Default Re: Focal Length Question.

    Quote Originally Posted by ShiNn View Post
    Hi guys,

    I have been asked by many people what does the 'mm' in the focal length means. I was stumped. Din know how to reply. Anyone able to help me out?

    i.e.
    17mm is wide angle.
    200mm is telephoto.

    what does 17mm means? like why term it in 'mm' ? how do they get the 'mm' ?
    325 posts and you still don't know? Maybe it's time to read up on the basic photography stickies in the newbies corner.
    Alpha

  4. #4

    Default Re: Focal Length Question.

    Quote Originally Posted by Rashkae View Post
    325 posts and you still don't know? Maybe it's time to read up on the basic photography stickies in the newbies corner.
    why did they equate wide angle with 17mm? what does the 'mm' means? has it got to do with the degree of wide-ness?

  5. #5

    Default Re: Focal Length Question.

    i guess this is my qn proper. sorry first thread i did not state clearly. any pros?

  6. #6

    Default Re: Focal Length Question.

    Quote Originally Posted by ShiNn View Post
    i guess this is my qn proper. sorry first thread i did not state clearly. any pros?
    Its not the degree of wideness that gives you the "mm". It used to be the distance between the lens element and the sensor/film of the camera but in today's multiple lens elements in a single lens unit, that method doesn't apply, however we still stick to the "mm" system to identify focusing distance. Hope i didn't say it too confusing.
    Last edited by spree86; 7th September 2010 at 12:28 AM.

  7. #7
    Member Irvine's Avatar
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    Default Re: Focal Length Question.

    Quote Originally Posted by ShiNn View Post
    i guess this is my qn proper. sorry first thread i did not state clearly. any pros?
    http://************/yjzfcu2 <-- go read it up. if still dun understand, search for more articles in google regardin focal length.
    Google is your friend. Make use of it.

  8. #8

    Default Re: Focal Length Question.

    i think i got it. its not the focal length. its called the angle of view.

  9. #9

    Default Re: Focal Length Question.

    http://en.wikipedia.org/wiki/Angle_of_view

    this is what i am looking for. thanks guys

  10. #10

    Default Re: Focal Length Question.

    Quote Originally Posted by ShiNn View Post
    why did they equate wide angle with 17mm? what does the 'mm' means? has it got to do with the degree of wide-ness?
    In a way yes. Basically it's saying that the focal point is 17mm in front of the sensor. This then equates to the angle of view, or how "wide" the angle of view is.
    Alpha

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