hyperfocal distance

Discussion in 'Medium Format Cameras and Accessories' started by CPorter, Oct 16, 2005.

  1. CPorter

    CPorter Member

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    I have an issue with determining the hyperfocal distance on my RB67 90mm lens. It uses bellows focusing with the distance scale on the side of the bellows. When I use an on-line HF distance calculator, I can't seem to get the same range of "in focus" distnace on my lens as the calculator is providing, leads me to think that surely, I am doing something wrong.

    Example: calculator parameters are --- 90mm, f/32, 6x7 format, .06 CoC to provide a HF distance of 14 feet giving a DOF range from 7 feet to infinity.

    My steps I take with my lens (the "ft" and "m" scale is a dial on the front of the lens and is manually operated, I guess since the focused distance scale is on the bellows, the only thing i can do is move the dial to put the infinity mark where it should be relevant to the f/stop I'm using):

    I put the infinity mark of the "ft" and "m" dial on the f/32 index, the red line on the lens should indicate, I think, the HF distance, it says 10 ft, and the other f/32 index mark on the lens should indicate, I think, half the HF distance from the film plane to the actual HF distance point of 10 ft, and, indeed, it does read half at about 5 feet.

    So, am I doing something wrong here. I thinking that since the distance scale for the lens is a separate operation from the lens itself, that maybe I'm doing something wrong. Thanks for any and all constructive comments.

    Chuck
     
  2. haris

    haris Guest

    Chuch, why use on-line HF calculator? I mean, if you have on lrns HF calculator use that. It should be accurate for that lens.

    Set infinity on f32. See what distance is on focus mark. That is hyperfocal distance for your lens for f32. On oposite f32 mark is closest distance which will be in focus. For example 3 meters (9 feets). So, everything from 3m (9 ft) to infinity will be in focus when you close aperture on f32. Same procedure for any aperture opening. SO, no need for on-line hyper focus calculator.

    Hope I didn't made mistakes when writting this :smile:
     
  3. Lee L

    Lee L Member

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    Have you checked to see that the bellows scale presumes the same CoC as the online calculator? If they have a different CoC, the results will differ. If they don't, you can probably figure out the CoC of the bellows DoF scale by plugging in different values of CoC online until the online calculator agrees with your lens.

    If you want a smaller CoC than the bellows scale, you can just use the markings for an appropriate aperture that's a bit more demanding, say shoot at f:16 but use DoF markings for f:11. Use the online calculator to check what the revised CoC is.

    I find that on many cameras, I find the DoF chosen by the mfgr to be too loose, i.e. they allow for more unsharpness than I like. So I often pull back a stop or so on the DoF scale, shooting f:16 at hyperfocal for f:11, etc.

    Lee
     
  4. waynecrider

    waynecrider Member

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    When shooting an SLR such as the RB, Hassy or Rollei, I just stop the lens down and look at the DOF when focusing. I change the shutter speed till I get my exposure right. It's much easier to see then on a 4x5.
     
  5. CPorter

    CPorter Member

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    Lee,

    I plugged in several different CoC values and found that a value of .085 provides a HF distance that most closely replicates the indication on my lens. Thanks for that information.

    Chuck
     
  6. Lee L

    Lee L Member

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    Chuck,

    Check here http://dfleming.ameranet.com/ for a couple of programs that generate hyperfocal charts and DoF dials for field use. They run under Windows and you get to choose the CoC to suit your preferences.

    Lee