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Thread: Fixed focus 4x5 camera

  1. #1

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    Fixed focus 4x5 camera

    Hi,

    Recently I picked up a sinar camera with a bunch of lenses. Including a sinaron F5,6 65mm lens. Now I want to try a simple fixed focus camera with this lens. My reasoning that the DoF will be big enough to do without a focusing system. Is my thinking correct?

    Peter
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  2. #2
    Jac@stafford.net's Avatar
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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Degroto View Post
    Recently I picked up a sinar camera with a bunch of lenses. Including a sinaron F5,6 65mm lens. Now I want to try a simple fixed focus camera with this lens. My reasoning that the DoF will be big enough to do without a focusing system. Is my thinking correct?
    It depends upon how critical you are. The rest is physics you can get from a DOF table - how close, what aperture, degree of enlargement.

  3. #3

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    Re: Fixed focus 4x5 camera

    Of course you can. The quality will depend on the depth of field that is acceptable to you and the distance that you shoot from. The 45 Linhof Aero Technica EL used lenses from 90mm up and the 90 was in a fixed focus mount. Of course, being an aerial camera,meant that the minimum legal altitude is 500'.

  4. #4

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    Re: Fixed focus 4x5 camera

    Physically possible? Of course. Wise? Doubtful unless, as Bob suggested you focus the camera for a distance -- aerial cameras are focused on infinity -- and then use it only at that distance.

  5. #5
    Drew Bedo's Avatar
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    Re: Fixed focus 4x5 camera

    Be on the look out for a TravelWide. It was originally designed as a fixed focus 65mm camera.
    Drew Bedo
    http://www.artsyhome.com/author/drew-bedo




    There are only three types of mounting flanges; too big, too small and wrong thread!

  6. #6
    Jac@stafford.net's Avatar
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    Re: Fixed focus 4x5 camera

    If the OP is interested I can post one of my 6x10cm cameras (Plaubel Veriwide) which zone focuses, but with an attached compact laser rangefinder it can knock-on focus. There is no reason it would not work with 4x5". I've made no pictures of it yet.

    Aside, I'm upgrading my 4x5" cameras which have earlier 47mm Super-Angulons to 47mm Super-Angulon XL. Not finished. Here are the 'before' pictures. First the f/8, and another (f/5/6). (Yes, that's 4x5). Both are in focusing mounts.

  7. #7

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    Re: Fixed focus 4x5 camera

    Hi Jac that would be awesome. The idea of fixed focus for me comes from street photography where you use aperture f/16 for example and focus the camera that everything is sharp between 1,5 meters to infinty. I want to use that principle for my camera. Also I use an old Eho boxcamera that is more or less sharp from 3 meters onward. I should be able to achieve something like that with my fixed focus camera. Maybe not but I wil have become a wiser man after that (haha).

    From where do I measure de focal lenght of the lens? From the plate where the lens is attached?
    Stupid questions deserve stupid answers.
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  8. #8

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    Re: Fixed focus 4x5 camera

    From where do I measure de focal lenght of the lens? From the plate where the lens is attached?

    Hello from France!

    This is a frequently asked question

    What you want is to set the proper distance between the lens mount and the film.
    Hence, to do this, the knowledge of the focal length is not really useful, as strange as it may seem!
    What you need is a distance given by lens manufacturers, named "flange focal distance" or sometimes "Flange Focal Length" (e.g. in Fuji lenses documentation).
    This is the distance between the back side of the shutter and the focal point. The focal point is where an image of a far-distant object is projected sharp.
    Now in order to properly set your lens mount in front of your film holder, you have to take into account the film holder's depth, which is for modern film holders compliant with the ANSI standard
    - 2" x 3" and 4" x 5" : 5.0 mm +- 180 microns (0.197" +-0.007")
    - 5" x 7" : 5.8 +- 250 microns (0.228" + - 0.010")
    - 8" x 10" : 6.6 mm +- 400 microns (0.260" + - 0.016")

    If you already have a springback with ground glass, simply focus the image of a distant object, no computation is required.

    And if you wish to fix-focus at the hyperfocal distance, instead of infinity, starting from the flange focal distance, you'll need to slightly increase the length between the lens and film by a small amount, to be easily computed according to your working f/number, focal length and sharpness criterion.

    You can have a look at this article (in French) by Gilles Barbier who built a fix-focus camera for the 5x7" format.
    http://www.galerie-photo.com/barbier-hybis-90.html
    In this case, focal length was 90 mm, the sharpness criterion was 150 microns, the working aperture f/16, hence the offset required to focus at the hyperfocal distance instead of infinity was 3.3 mm.

  9. #9

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    Re: Fixed focus 4x5 camera

    Emmanuel, published flange-focal distances are nominal. So are the focal lengths engraved on lenses. A lens' design focal length -- the focal length if the lens matches its prescription -- can differ from the nominal. Example, the 260/10 Process Nikkor. Its design focal length is 267 mm. And actual focal length can differ from design. Example, the 38/4.5 Biogon. Design focal length 38.5 mm, actual focal length of the twenty (20) I've had as measured by the original customer ranged from 38.3 to 38.8 mm.

    The OP is going to have to get his lens, decide the distance at which his fixed focus camera should be focused, measure his lens' flange-focal distance when focused at that distance and then build his camera.

  10. #10
    Jac@stafford.net's Avatar
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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Degroto View Post
    Hi Jac that would be awesome. [...]
    I do not have the digital camera today to offer a snapshot so let me just briefly describe the set-up.

    The key part is a Bosch GLR225 laser distance meter that I used in construction work. It is small & handy. (Shop carefully. Prices are all over the map).

    The meter has a 1/4" tripod socket. I have mine in an L-bracket that places it on the side of the camera (a Plaubel Veriwide). It has four different measurement reference points - #1 from its front, #2 from the tripod socket location, #3 from the bottom and #4 from a point a couple inches rear of the bottom. Forget about #4. Just mount the meter so that any from 1-3 locate at the film plane. It is easy with a bracket. I use #2 and it's about perfect.

    I can trigger the laser from my left hand and see the laser dot in my viewfinder. It does not work trying to see the dot on a ground glass for good reasons (light frequency mainly & brightness). I use viewfinders on most of my cameras.

    Good news - it is good to about 225' and is accurate. Bad news - it does not work well in bright sunlight without a special target placed at the subject. It is also not good for pointing at a subject's eye. Don't do that.

    So, surf for Bosch GLR225 laser distance meter and instructions to get the whole idea. Hope this helps. Will get a snapshot soon.

    EDIT - Dan Fromm's advice is right-on and suggests a more cost effective approach. One thing I did with a 4x5" box camera with a sprung rear door was to drill a hole in the middle of the back, then took a spare 4x5 holder, removed the two slides and drilled a hole in its center, then used a lope to aerial focus on various distances and jot down the distance shown on helical focus mount. With a wide lens you can probably note a few significant distances and use DOF to take care of the rest.

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