light and f stop

Discussion in 'Medium Format Cameras and Accessories' started by bohica, Sep 4, 2005.

  1. bohica

    bohica Member

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    Will a 110mm f2.8 give the same shutter speed (in same lighting sitiation) as a 80mm f2.8
     
  2. Claire Senft

    Claire Senft Member

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    Yes.
     
  3. Paul Sorensen

    Paul Sorensen Subscriber

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    Just so you know that there is a consensus out here, yes as well.
     
  4. bohica

    bohica Member

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    thanks paul and Clare. I thought it would but I try not to get to much into the tech side of photography, it reduces some of the fun for me
     
  5. Ole

    Ole Moderator Staff Member

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    That's not "the tech side of photography", it's basic knowledge.

    ALL lenses will let in the same amount of light, thus giving the same exposure with the same shutter time under the same lighting conditions. That's why they all use the same numbers.
     
  6. joeyk49

    joeyk49 Member

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    Not a stupid question...I pretty much made the assumption, but, having no formal photog training, wasn't rock solid on the matter; glad you asked and were answered. 2.8 is 2.8 is 2.8.......
     
  7. Dan Fromm

    Dan Fromm Member

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    bohica, craft precedes art. If you want to produce the results you want, not some random who knows what, you're going to have to master the craft. That means learning technique.

    Sorry, that's how it is,

    Dan
     
  8. Claire Senft

    Claire Senft Member

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    It is probbably a good time to explain what an fstop means. F stands for fraction. If you use a 100mm lens at f4 then the fstop is 1/4th of th focal length or 25mm. If you set f8 on a 50mm lens then the fstop is 1/8 the focal length or 6.25mm.


    The f stop markings are computed with the lens focused at infinity. If you focus at a distance of less th 8 focal lengths away you have to start allowing for the fact that your lens's fstop markings are sufficiently different from infinity and allow for it.

    That is enough lesson for the day.
     
  9. bohica

    bohica Member

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    i know what f stops are, been amerture or pro for over 30 yrs, just didn't know if the longer focal length would change the amount of light even though the opening was larger, you guys belong on betterphoto.com, ask any question there and you'll get forulas to figure it out, i now photo for FUN, if you can't handle that then don't read my post
     
  10. Dave Parker

    Dave Parker Inactive

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    even though the opening size on a longer lens is larger, in theory based on the standarization of the f/stop, the light reaching the film will be the same, hence the same shutter speed for the same exposure as a shorter lens, there are variables that come into equations based on how true the aperture is based on the manufactures tolerances, but yes, an f/stop is a f/stop across the broad range of lenses.

    Dave
     
  11. BradS

    BradS Subscriber

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    Yes. This is the genius of f-stop. It is a measurement of the daimeter of the aperature relative to the focal length of the lens. With regard to the amount of light that reaches the film, f-2.8 is f-2.8...regardless of the focal length.
     
  12. gnashings

    gnashings Inactive

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    I don't understand why you got so defensive. You asked a question. You were answered. It was a very basic question - so many assumed you were not aware of the basic theory behind it... and what do you know- explained it to you.
    I've literally asked dozens of questions on these pages, and have recieved nothing but kind and thoughtful replies. Such as you recieved based on the question you asked. Perhaps the only person here that has any trouble handling anything is you - like the fact that the answers you recieved were very fitting to the level of knowledge you showed in your question.
    I find it in very poor taste to lash out at people who take time to help you out just because you are insecure about your own abilities. Smarten up and appreciate this community - you would be very hard pressed to find a more helpful one anywhere - instead of pointing out who does and does not belong here! You can be assured that this kind of attitude only puts one persons "belonging" in question...
     
  13. bohica

    bohica Member

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    sorry gnashings , only 1 reply was short and egotitical and having gotten so many of those from the other site I over reacted, yes, I have gotten some good answers on here, i got out of the pro bussiness because using formulas for figureing the size of the extension ring similar things took all the fun out of photoraphy for me, plus i spent all my time taking photos for other people of what they wanted, i have a friend that had rather do that type of stuff than actally take the photo, not me. my main reason for asking the question was i have 2 lenses, a 110 and 80, both 2.8, and it just seems odd that the mfr would make 2 lenses so close in focal length with the same max opening unless possibley the 80 let in a little more light. I don't need to learn a craft, i'm retired and do this for fun and relaxation, nothing more
     
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  15. Dave Parker

    Dave Parker Inactive

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    Actually it is not that uncommon at all to see two lenses that close in focal length, many of the medium format companies do this, the 80mm is what is normally considered the normal and is used as a kit lens, the 110 often times is used as a people taking lens, the small amount of extra focal length, allow you to step back a bit and not have the big nosed look to your frame filling head shots.

    Heck if I remember right Mamiya has an 80, 105, 110 and then a 150 in their lineup..

    Dave
     
  16. Nick Zentena

    Nick Zentena Member

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    Bronica at one point was selling

    40mm,50mm,60mm,75mm,105mm,135mm,150mm,180mm and 200mm. That's no more then 30mm between lenses. Many closer then that. They have some differences. Off the top of my head the 150mm focuses closer then the 135mm or the 180mm and is a touch faster. But not anything major. You got to choose your favorite focal length.

    Later they yanked the 105mm and replaced it with a 100mm macro lens. I'm not sure I understand this one since it doesn't focus very close. Maybe I'm missing something.
     
  17. gnashings

    gnashings Inactive

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    This is just a guess, but I think the reason is a combination of technical pursuits (improving the product, trying new solutions, etc - I am far from a lens design guru, but from what I understand,there are design differences, lenses being optimized for different applications, etc.) and.. well, marketing. There seem to be fewer "buy what I need" types out there than victims of "oh! I need that!" (myself often in that second group, despite my better judgement :smile:)
     
  18. bohica

    bohica Member

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    ok, when i bought my m645 it came with the 80, when i got the 645 1000s it came with the 110, i would think maybe the DOF might be a little narrower with the 110
     
  19. Dave Parker

    Dave Parker Inactive

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    Depth of field always decreases when focal length increases, I shoot alot with big glass on 35 when doing wildlife work and the longer the lens the shorter the DOF which requires much more precise focusing, but the DOF between a 80 and a 100 is going to be very little. And the 100 you got on your 1000s was not the standard kit lens, the 1000s came with the 80 as well.

    Dave
     
  20. Dan Fromm

    Dan Fromm Member

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    Sigh. DOF is controlled by magnification and aperture, focal length has nothing to do with it. There's a widely-held misperception that longer lenses give less DOF than shorter ones. True, if one takes the same, but narrower, picture with the longer lens from the same shooting position, but the reason this happens is that the longer lens is giving higher magnification. Step back with the long lens to get the same magnification and you'll get the same DOF.

    And there's one slight exception that seems, at least to me, to have little practical significance. If the subject is, at the desired magnification, more-or-less at the short lens' hyperfocal distance from the camera then at that magnification the short less will get more DOF than the long one. Do the arithmetic. But that's a very special situation.

    Cheers,
     
  21. Ed Sukach

    Ed Sukach Member

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    Not quite. "f" (lower case) is the standard symbol for focal length.
    Properly, the aperture should be written as "f/stop" Where "f" = focal length divided by "stop" = aperture diameter.

    It is a ratio. Equal numeric f/stops transmit equal amounts of light.
     
  22. Ed Sukach

    Ed Sukach Member

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    Did I miss something? I thought bohica asked a relatively simple question about "f/stops". Where did s/he request information about "mastering photography"?
     
  23. lee

    lee Member

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    In a post on the first page of this thread Bohica said this, "thanks paul and Clare. I thought it would but I try not to get to much into the tech side of photography, it reduces some of the fun for me". To which Dan Fromm replied what you quoted.

    lee\c
     
  24. Ed Sukach

    Ed Sukach Member

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    I know that, Lee. It is, to me, dangerous to answer an unasked question.
    It came across - to me -as, "You asked about f/stops? You know, you really must master photography!"

    Hey ... that would be a good question ... "How do I Master Photography?"

    Anyone want to take a stab at that one? Answers must be not more than three words in length.
     
  25. Soeren

    Soeren Member

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    How do I Master Photography

    KIS(S)
    Søren
     
  26. Dave Parker

    Dave Parker Inactive

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    Dan,

    Focal length equates manification, which in shooting the same subject at the same distance you will have less depth of field, one other way to increase magnification is macro extention tubes, or special close focus designs, which will also yield less depth of field, which of course is a different subject.

    Dave