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Thread: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

  1. #1

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    Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    If any forum members have used either Lotus or Chamonix film holders with their Korona 12x20 camera, could you please comment on compatibility in practice?

    I know both the Lotus and Chamonix dimensions are slightly different from the original Korona holders, including T-distance, but I would very much value any accounts of first-hand experience using these particular holders with a Korona 12x20. Was the focal plane registration noticeably off? Did the holders move too much when inserted in the back? Were the results satisfactory?

    Thank you in advance!

  2. #2

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    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    I’ll answer my own question by way of follow-up for others who may be interested.

    I have been looking to acquire additional 12x20 holders for my Korona for over a year. Virtually no original Korona holders became available on the used market, so I resolved to buy new.

    Based on reviews and Korona-compatibly, my first choice was AWB (filmholders.com). However, over the course of a very intermittent six-month correspondence, Alan was never in a position to take my order. I got tired of waiting in vain and wrote to Chamonix and Lotus for their 12x20 film holder dimensions to assess compatibility with my Korona. Here’s a quick comparison of the critical dimensions (in mm):

    Korona Lotus Chamonix
    T-Distance 9.27 8.35 9.8
    Rib lock dist. 553 550.5. 550.3
    Width 355.6 355 345.8
    Thickness 19.6 18 20.6

    I chose the Chamonix largely because I would rather shim my ground glass slightly to attain the proper T-distance than irrevocably mill it down a millimeter to match the Lotus.
    The Chamonix’s unibody carbon fiber dark slides were another major attraction. Inserting and removing 12x20 dark slides is prime time to cause bending or, heaven forbid, cracking, and the wooden pull tab on ULF dark slides can represent an Achilles heel. Lastly, although the springs on my Korona’s 12x20 back are still peppy, I thought I would get better tension using an ever-so-slightly thicker film holder (the Chamonix) than the thinner Lotus.

    Within a week of resolving to go with the Chamonix, I had the film holders in hand! Hugo is simply excellent to work with, and the shipping and packaging exceeded my expectations.

    I loaded the Chamonix holders and made test exposures with and without strips of 0.5mm plastic shim stock placed under my ground glass. The shimmed results show perfect alignment between focus on the film and the ground glass (frankly, the unshimmed results are only the tiniest bit off).

    The Korona back holds the Chamonix holders securely in place. Insertion and removal is a dream, and the rib lock fits securely into place. My test negatives show the arrangement to be light tight; no hint of any light leaks.

    The fact that the Chamonix holder is about 10mm narrower than the original Korona holder means that the rebates on the film are not identical: one is slightly thicker than the other. I had planned to slip a 5mm aluminum bar under the Chamonix film holder to frame it perfectly symmetrically in the opening of the Korona’s back, but after seeing how little impact the width difference has on the negative, I don’t think that I’ll bother.

    To sum up, Chamonix film holders are a great option for Korona 12x20 cameras. For optimal compatibility, shim the Korona’s ground glass by 0.5mm to match the Chamonix holder’s T-Distance.

  3. #3
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    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    Thanks very much for taking the time to share your findings.

  4. #4

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    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    Ditto what Oren said, very useful; btw did you have a look at S&S dimensions as well? Curious about compatibility between S&S and Chamonix. Is the rebate wider on the Chamonix or Korona? Show us what the gear looks like! Thanks

  5. #5

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    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    Sorry, this was by no means a comprehensive survey of 12x20 film holders, and I did not consider S&S. Perhaps others can volunteer some firsthand accounts.

  6. #6

    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    The standard "t" measurement for a 12 x 20 , 8 x 20, 16 x 20, 20 x 24 is 0.355. You have to remember these cameras were made back in the 1920 to the 1940's and we here in the US used the inch system at that time and is still used today to make these holders and cameras.

    There are 3 manufactures of holders in the US that made holders to fit your camera one was Allan as you said he is not very helpful, S & S holder fit and were based on the Korona holders but they are no longer making holders. Plus there is one still making holder to fit your camera.

    There is one thing you need to know about holders for this size camera there are two different distance for the rib lock. The standard being use by Canham and myself is 21.600 this is from the flap end to the far side of the rib lock. The end flaps also varied a bit. Basely when you bought this camera new it came with 3 holder to fit the camera. So there are variation on the measurements of the holders. The one thing that stayed the same on this camera is the width of the holder. Max is 13.96 inches.

    Her a link to a page with the measurements. http://www.lg4mat.net/FilmHolderSpects.html
    Richard T Ritter
    www.lg4mat.net

  7. #7

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    Re: Korona 12x20 compatibility with Lotus or Chamonix Film Holders?

    Thank you, Richard, your expertise and services should have been on my radar as I was considering holders.

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