Results 1 to 9 of 9

Thread: f/stops

  1. #1

    Default f/stops

    Hi everyone,

    i have searched on google about what is stop down 2 fstop. But too chim to understand.

    for example, my 50mm lens f1.8.

    2 stop down from f1.8, what is the fstop ? I seen the formula but very complicated.

    anyone have a simple way to calculate ?

  2. #2

    Default Re: f/stops

    U can try googling for it

    http://en.wikipedia.org/wiki/F-number

    1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22

    Those are the typical 1 stop difference. Anything in between would be 1/3 or 1/2 stop difference, depending on ur camera.

    1 stop difference means half the light of the previous stop. So basically, at f/1.4 you will get half the light of f/1. And at f/2, it will be half the light of f/1.4 and one quarter the light of f/1.

    To ans ur qn, 2 stops below f/1.8 would be f/3.5
    Last edited by yc2005; 9th October 2009 at 04:06 PM.

  3. #3

    Default Re: f/stops

    so simply it means, if my camera is set to 1/2 stop. to get to 1 stop from the fstop, i dial 2 times, for 2 stop i just turn the dial 4 time.

    in short,

    1/2 + 1/2 = 1
    1/2 + 1/2 + 1/2 + 1/2 = 2

    am i right ?

  4. #4

  5. #5
    Senior Member ZerocoolAstra's Avatar
    Join Date
    Mar 2008
    Location
    rainy Singapore
    Posts
    9,523

    Default Re: f/stops

    i don't suppose you want to know why f/1.4 ---> f/2 (and not f/2.8) is 1-stop (i.e. halving the aperture size)...... hahahaha
    Exploring! :)

  6. #6

    Default Re: f/stops

    Quote Originally Posted by iczboi View Post

    anyone have a simple way to calculate ?
    it is far easier to just keep working with f-stops

    after a while you just get used to it, at least the part that matters to what you shoot.

    for example, i am more familiar with small aperture side.. because i shoot landscapes.

  7. #7
    Moderator ziploc's Avatar
    Join Date
    Jan 2002
    Location
    Snoopyland
    Posts
    4,577

    Default Re: f/stops

    Actually it is very easy to remember the f numbers. Just remember 1 and 1.4. The rest are just x2 of these 2 numbers.

    So:
    1, 1.4
    2, 2.8 (because 1x2=2, 1.4x2=2.8)
    4, 5.6
    8, 11
    16, 22

    Each of the above is 1 stop from the next. So f/1 to f/1.4 is one stop, f/1.4 to f/2 is one stop, and so on. The bigger the number, the smaller the aperture (just take f as a constant, e.g. 1. So 1/8 is smaller then 1/11, for example). Stop down means to reduce the aperture. So stop down 2 stops means reducing 2 stops. You can easily find that out from the aperture numbers listed above.

  8. #8

    Default Re: f/stops

    Quote Originally Posted by ziploc View Post
    Actually it is very easy to remember the f numbers. Just remember 1 and 1.4. The rest are just x2 of these 2 numbers.

    So:
    1, 1.4
    2, 2.8 (because 1x2=2, 1.4x2=2.8)
    4, 5.6
    8, 11
    16, 22

    Each of the above is 1 stop from the next. So f/1 to f/1.4 is one stop, f/1.4 to f/2 is one stop, and so on. The bigger the number, the smaller the aperture (just take f as a constant, e.g. 1. So 1/8 is smaller then 1/11, for example). Stop down means to reduce the aperture. So stop down 2 stops means reducing 2 stops. You can easily find that out from the aperture numbers listed above.
    cool, this makes it clearer now...

  9. #9
    Moderator ziploc's Avatar
    Join Date
    Jan 2002
    Location
    Snoopyland
    Posts
    4,577

    Default Re: f/stops

    Erm mixed up. f/11 is smaller then f/8. Just discovered this mistake.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •