Graflex reflex or other LF patent #'s

Discussion in 'Camera Building, Repairs & Modification' started by Murray@uptowngallery, May 10, 2006.

  1. Murray@uptowngallery

    Murray@uptowngallery Member

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    I also posted on Graflex.org, but responses there are less-DIY humoring (just posted).

    If anyone has a reflex type Graflex camera that has patent numbers on it, would you mind passing them along. I want to study the mirror method vs prism.

    Thanks

    Murray
     
  2. Dan Fromm

    Dan Fromm Member

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    Prism? What prism? Graflexes don' have no steenkin' prism.

    And more to the point, SLRs that use a prism in the viewing system don't place it between lens and film plane. They place it on top of a ground glass that's as far from the film plane as the film is.

    If you read french, there's a discussion on http://www.galerie-photo.info/forum/, see http://www.galerie-photo.info/forum/read.php?f=1&i=8982&t=8982 ,
    about a 4x5 Arca Swiss Reflex that's now on eBay. In it Emmanuel Bigler describes how the mirror and shutter release are actuated. The information may be of interest.
     
  3. Murray@uptowngallery

    Murray@uptowngallery Member

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    Yass, so the mirror tosses the photons against a ground glass then the prism does it's magic.

    I am mechanically dyslexic, I think, so I am still disturbed (I'm not done yet) by the thought of a 45 degree mirror illuminating a ground glass that's not parallel to it. Obviously it works, and I just sketched it out (about time, it's been a year since I thought of trying this) and convinced myself that long + short path at the bottom of the mirror = short + long path at the top, and it all works out on the ground glass. There, I feel better now. Good thing someone invented pencils, as I don't have any charcoal and grease in my cave. That's a reference to me dropping my Neander-cam (there's not enough known artistic knowledge about that group) plans and rethinking it as Cro-Magno-Cam.

    I'll try Altavista Babelfish for that link. It'll be better than my French. (I read Asterix & Obelix comics in French in Spanish class...I don't know what our teacher was thinking.

    Thanks
     
  4. Murray@uptowngallery

    Murray@uptowngallery Member

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    OK , no need for patent #'s now.

    Single mirror prototype worked...now to see if I can add a rear-facing viewfinder, then...
     
  5. John Koehrer

    John Koehrer Subscriber

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    Murray,
    How about a 2nd mirror at 45 degrees ala a kids periscope?
     
  6. Donald Qualls

    Donald Qualls Member

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    Problem is, if you just put a second mirror above the ground glass so you're looking forward (same direction as the lens), you're back to a right-reading, but inverted view. If you can get two first surface mirrors perfectly aligned in a "roof", you'll have 2/3 of a pentaprism; use that roof to reflect the light approximately "over" the front edge of the ground glass, and catch it there with another flat mirror, angled to let you look parallel to the lens axis, over the ground glass. The view in that mirror will be upright and right-reading, and if still too close for aging eyes, you can add a mild diopter as an eyepiece.

    And then you'll have made the leap between the first SLRs dating back to around WWI, and the Contaflex of the late 1930s: eye level viewing and focusing.

    Personally, for large format, I'd rather have a chimney hood like the ones on Graflex and Soho Reflex. Can't see doing too much hand holding with a heavy SLR anyway; may as well optimize for tripod use.
     
  7. Murray@uptowngallery

    Murray@uptowngallery Member

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    chimney

    That's the part I couldn't understand...big camera, big tripod, short photographer...the camera has to be THAT much lower to view from above, oh, wait...single mirror, hold camera upside down like you're in a crowd, and...oh, it's still inverted...
     
  8. Donald Qualls

    Donald Qualls Member

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    If there's a problem with the tripod going no lower and your legs going no higher, then you're probably ahead to reinvent the pentaprism. You might check at Surplus Shed and Anchor Optical for "roof prisms" -- these have the reflecting faces already at the correct angle so you get the inversion (if you can find one large enough) and just need a mirror for the front side of your ersatz pentaprism. Careful positioning of components will let you reject the spurious reflection(s) from the front face of the roof prism...

    Alternately, you could use two separate mirrors in place of the roof configuration; that would allow individual adjustment and you wouldn't have to try to adjust out the seam, but would stretch the optical path a bit (so you wind up using a weak telescope to view the ground glass -- possibly not a bad thing).
     
  9. tkevans

    tkevans Member

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    Patent number for the two-mirror Auto Graflex

    Murry, You may find this patent interesting. 843140 Feb 5, 1907. It is for the Auto Graflex that had an accordian viewing hood and a second mirror on the underside of the lid. One could view the ground glass either by looking directly down through the hole in the hood or by looking forward at the second mirror.
     
  10. waynecrider

    waynecrider Member

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    A few years back I ran into a guy flying a helium balloon/dirigible with a Pentax 645 hung under it on a moveable platform. He was photographing some property from above for a developer. I guess it was cheaper then hiring a plane. Anyways, he had a camera hooked up to the GG and a small monitor on what could be considered a yoke to handle the balloon and as a mount for the screen. It was a neat setup and after that I always wondered about pointing a small CCD camera at a GG with a small video monitor to view upside down. Btw, this guy's business was a franchise which still may be available.
     
  11. Dan Fromm

    Dan Fromm Member

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    Wayne, back when the Beaulieu 8008 was still being made (AFAIK Beaulieu is gone), Super8 Sound offered a video tap, so-called, for it that was similar in concept to what you described. A little CCD video camera that screwed in in place of the eyepiece.