down and dirty of fstops

Discussion in 'Photographic Discussions' started by mysteryscribe, Dec 20, 2006.

  1. mysteryscribe

    mysteryscribe TPF Noob!

    Joined:
    Feb 1, 2006
    Messages:
    6,071
    Likes Received:
    3
    Location:
    in the middle of north carolina
    Can others edit my Photos:
    Photos OK to edit
    f stops are also called aperture settings. Actually the smaller the number on the scale the larger the opening of the aperture.

    Why you ask? You didn't ask? Well hell I'm gonna tell you anyway. The number are actually the demoniator of fractions. Yep f2.8 is acutally 1/2.8 or almost all of the total opening size in play. f16 is actually 1/16 or a much smaller part of the total in play.

    Think of it this way would you rather have 1/16 of a million dollars or 1/2.8 of a million dollars. See now isnt that simple. There are some formulas to figure how the number are derived but I never bothered to learn them.

    Remember the faucet... well it is going to come into play again. Just remember the smaller the number on the scale (or the larger the fraction) the higher the volume of light.
     
  2. Big Mike

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

    Joined:
    Dec 16, 2003
    Messages:
    33,821
    Likes Received:
    1,811
    Location:
    Edmonton
    Can others edit my Photos:
    Photos NOT OK to edit
    Don't forget to mention that the faction (ratio) in question is the focal length over the diameter of the aperture. So if you have a 100mm focal length, and your F stop is F4...the diameter of the aperture is 25mm.

    Also, when we look at F-stops on a scale
    f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128...
    the F numbers don't increase in a linear fashion. In other words, F8 is not twice as much light as F16. They increase by a factor of 1.414 (square root of 2).
     
  3. mysteryscribe

    mysteryscribe TPF Noob!

    Joined:
    Feb 1, 2006
    Messages:
    6,071
    Likes Received:
    3
    Location:
    in the middle of north carolina
    Can others edit my Photos:
    Photos OK to edit
    Thats why I hope everyone will jump in... Believe it or not I don't know it all and can't remember to state all I do know thank god. I'm boring enough already.
     
  4. oldnavy170

    oldnavy170 TPF Noob!

    Joined:
    Sep 7, 2006
    Messages:
    2,236
    Likes Received:
    0
    Location:
    Rochester, New York
    Can others edit my Photos:
    Photos OK to edit
    So to get this straight. Do I get more light with a higher F number or a lower one?
     
  5. mysteryscribe

    mysteryscribe TPF Noob!

    Joined:
    Feb 1, 2006
    Messages:
    6,071
    Likes Received:
    3
    Location:
    in the middle of north carolina
    Can others edit my Photos:
    Photos OK to edit
    exposure (light on the film) is a function of both shutter speed and fstop.... but f4 is big opening and f16 is a small opening. Thats because they are the denominators of fractions not just number. 1/16 of a pie is less then 1/4 of a pie... Ie f16 is smaller than f4... again they work inconjunction with the shutter speed which is the next bit.
     
  6. ftops

    ftops TPF Noob!

    Joined:
    Dec 25, 2006
    Messages:
    21
    Likes Received:
    0
    at an identical shutter speed, there will be more light at a LOWER setting, because the hole is bigger. essentially you are getting closer and closer to a ratio of 1:1 as you open the aperture. in some lenses, if you have a depth of field previewer, you can hold it down and see the aperture close down or open to the specified setting before you take the picture.

    another analogy is the principle of volumetric efficientcy in an engine. if your engine has tiny intake ports, that air will come rushing in extremely fast, but it will be so confined that not much will get in. make the port bigger, and more air can flow in, but because of reduced pressure it will be moving slower. the solution to this for an engine is simple: a giant turbo! for a photograph...............photoshop, i suppose.
     
  7. dgs

    dgs TPF Noob!

    Joined:
    Nov 27, 2006
    Messages:
    85
    Likes Received:
    0
    Or a higher film speed.
     
  8. Buddhabuddha

    Buddhabuddha TPF Noob!

    Joined:
    Dec 15, 2006
    Messages:
    55
    Likes Received:
    0
    Location:
    Sunny Milwaukee Wisconsin
    Can others edit my Photos:
    Photos OK to edit
    This is all why i love photography. You can take the same picture hundreds of ways, and no 2 results will be quite the same. Similar, yes, but never the same.
     
  9. castrol

    castrol TPF Noob!

    Joined:
    Apr 26, 2006
    Messages:
    421
    Likes Received:
    0
    Location:
    Spring, TX
    I have removed one of my lenses before and showed a couple of people
    how the aperture really functions. You can cycle through the stops and actually
    see how the aperture opens and closes to allow or restrict more light. I know
    most of you know that... but I think some people might be afraid to tinker
    with their equipment just to see how it works...
     
  10. Soocom1

    Soocom1 TPF Noob!

    Joined:
    Feb 27, 2006
    Messages:
    533
    Likes Received:
    3
    Location:
    Southwest US
    Can others edit my Photos:
    Photos NOT OK to edit
    Remember that the funny looking "F" has always stood for 'Function' in mathematics.

    A correspondence in which values of one variable determine the values of another.*

    Or, simply put that whatever set of numbers that go in, can have ONE and only ONE answer.

    So say a perfect exposure is a '10' Anything higher in number is over exposed, anything lower, underexposed.

    What ever set of numbers of the shutter speed in relation to the aperture
    must always come out the number 10 in order to make a perfect exposure. .

    * http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLG,GGLG:2006-25,GGLG:en&q=define%3a+function
     
  11. lorrir

    lorrir TPF Noob!

    Joined:
    Sep 18, 2006
    Messages:
    14
    Likes Received:
    0
    Location:
    Upstate, SC
    I am a canon girl and I love my canon lense, my solution to this problem is to buy all of my lense with a fixed 2.8f. Problem solved. Now all I have to worry about is shutter speed, and ISO and WB and Noise and Memory and Batteries and so on and so on. LOL.
     
  12. Digital Matt

    Digital Matt alter ego: Analog Matt

    Joined:
    Jan 30, 2004
    Messages:
    5,346
    Likes Received:
    65
    Location:
    Santa Barbara, CA
    Can others edit my Photos:
    Photos NOT OK to edit
    You are a little confused I think. Lenses that are a "fixed" 2.8, (and this only applies to zoom lenses) means that their widest aperture is 2.8, no matter what focal length you are zoomed to. If you look at the Canon 70-200 f/2.8 L, it has a maximum aperture of 2.8, whether you are zoomed to 200mm, or 70mm.

    The Canon 75-300 f/3.5~5.6 has a maximum aperture of f/3.5 at the 75mm setting, but at 300mm, it has a max of f/5.6.

    All lenses have a range of f/stops that they can utilize, starting from their max, whatever that may be, and, depending on the lens, a minimum of usually f/22 or f/32, and every f/stop in between.

    It pays to learn them all.
     

Share This Page

Search tags for this page

down and dirty f stops