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Thread: 11x14 Fidelity Medical Film Cassettes - film registration distance

  1. #1

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    11x14 Fidelity Medical Film Cassettes - film registration distance

    I have been using 5 used 11x14 Fidelity Medical Film Cassettes with my 11x14 Charmonix. I regularly shoot at f/64 and have been pleased with the sharpness of my negatives. But then recently I read that the film registration distance (front of holder to surface of film) is different than that of regular 11x14 Photo film holders.

    Is this true? Something I should consider and worry about?

    Personally I worry more about film buckling and it not lying flat (ran into this problem once when shooting vertically pointed down with my 11x14 at relatively large apertures).

    thanks

  2. #2

    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Quote Originally Posted by Greg View Post
    I have been using 5 used 11x14 Fidelity Medical Film Cassettes with my 11x14 Charmonix. I regularly shoot at f/64 and have been pleased with the sharpness of my negatives. But then recently I read that the film registration distance (front of holder to surface of film) is different than that of regular 11x14 Photo film holders.

    Is this true? Something I should consider and worry about?

    Personally I worry more about film buckling and it not lying flat (ran into this problem once when shooting vertically pointed down with my 11x14 at relatively large apertures).

    thanks
    I experienced this issue with my Deardorff V11 and ended up solving it. To ascertain if it is an issue with your camera and specific film registration let me walk you through what caused me to challenge the two holders attributes and learn what I found out and then you can decide if it is a non event or something that you need to investigate further.

    I was West of Denver on My Evans and I was making a quasi macro image of some bristlecone pines using a 24" Fuji C lens that I know required a modest compensation for bellows extension because I was relatively close to the subject matter. With ULF cameras we all know that it is not hard to find oneself in a macro domain at the least conspicuous time and it is just a part of the process. I spent a good 15 minutes on the compensation to frame it just so and ensure precise focus on the ground glass and locked the camera adjustments down so that when stopped down to F45 it was all there sharp as hand full of razor blades. I used a Fidelity medical cassette to make the image and when I processed the negative and proofed the print it was clearly lacking in the sharpness department to the degree that I knew that something was awry. I immediately took my camera and two sets of film holders and two sets of camera GG backs (when I got my DeardorffV11 I had Richard Ritter build me one fitting my S&S holders and when Deardorff Camera Company opened up its doors I found an original V11 back that I acquired) to a friend that is a master machinist and a photographer to check out. I was using the Deardorff original V11 back when I made the image with the Fidelity holder that was unsharp.

    When he investigated the accuracy of the probe depth of the two GG backs and the film holders he concluded that the Richard Ritter camera back that was registered to the S&S holders was as precise as technically possible. Absolutely spot on. The Fidelity Medical cassettes and the original Deardorff V11 back was way off. I am not a machinist myself but I do remember that the fix involved placing thin metal shims in the camera back to move the GG out to allow it to register properly with the Fidelity Medical Cassettes. He also used his depth micrometer to conclude the the medical cassettes have a pronounced very minor amount of curvature in the face of the base of the holder that is likely a function of how the metal core cooled down when it was heat moulded. Because of the distinct difference in the probe depth I only use the S&S holders in the Ritter back and the Fidelity holders in the Deardorff back and all is sharp as hell in the results department.

    Here is the bottom line from a technical perspective for the photographer. If one had a minor amount of registration error in the holder to GG back marriage and this error remained within the force of confusion of your photography (the combination of infinity focus subjects with broadly "tolerant" focus lenses such that the error of the physical components never exceeded the tolerance of the optical parameters), you may never see the net effect in your photographic results. However should you decide to make a modest or a legitimate macro photograph like I opted to do the ugliness of the condition could bring this issue front and center rather quickly.

    At the end of the day I feel that given the price of sheet film it is very easy to have a machinist check your holders in your camera to make sure your registration is where it needs to be. Make sure that you put a sheet of the film you are shooting in the holder to measure to in the camera for the probe depth investigation. If it needs adjustment, then the good news is that you are using one type of holder and the issue is one dimensional. I would also advise doing some research on the circle of confusion for the format and the lenses you are using so that you can put into proper perspective what the machinist shares with you relative to your probe depth results. I consider this process prudent equipment check out based upon the fundamental lack of industry standards for the 11x14 format. 8x10 and smaller it clearly is no big deal because these formats have published specs.

    As to your issue with the film buckling on 11x14 that should also be an easy thing to check. Take the same piece of film that you use to give to the machinists to check your GG depth and put it in your holder. Pull the dark slide and hold it over your head. Push on the film and see if you can see if move in the center. My personal take on this issue is that most modern films are quite robust in the thickness department and resist buckling quite effectively. If you want to be sure that this issue goes away. put a piece of double stick tape in the center of your holder when you load it and push down allowing the tape to stick to the film. Problem solved.

    Hope this helps!

    Cheers!
    Last edited by Michael Kadillak; 25-Dec-2015 at 23:09. Reason: typo

  3. #3

    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Another issue I will share with you. You should only stop down as far as necessary to ensure efficient focus. F64 is not a prerequisite, just an option. It may be entirely possible to obtain efficient and complete focus stopping down to f32 then there is not reason to stop down any further. I have made blazingly sharp 11x14 negatives at f22 if your camera movements are where they need to be optimally. The need to adjust to wind or water movement is usually the driver in this condition. Again, I go back to when you have a GG set up that is accurately optimized and checked, you can make a single negative knowing that you have left nothing to chance.

  4. #4

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    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Borrowed a depth gauge from a friend and measured what I call the film registration distance on one of the Fidelity Medical Film Cassettes (with a sheet of film in the holder) and same measurement on the back of my Charmonix 11x14. Took several measurements all around and they were all within less than the thickness of a sheet of Bergger 200 11x14 sheet film. Also measured the thickness of sheet of Bergger 200 film and a sheet of X-Ray film... the Bergger was 3 times thicker than the X-Ray film.
    Agree with "only stop down as far as necessary to ensure efficient focus", but since I'm contact printing the film, I like to stop down even further to cover any focusing error on my part.
    Greg

  5. #5

    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Quote Originally Posted by Greg View Post
    Borrowed a depth gauge from a friend and measured what I call the film registration distance on one of the Fidelity Medical Film Cassettes (with a sheet of film in the holder) and same measurement on the back of my Charmonix 11x14. Took several measurements all around and they were all within less than the thickness of a sheet of Bergger 200 11x14 sheet film. Also measured the thickness of sheet of Bergger 200 film and a sheet of X-Ray film... the Bergger was 3 times thicker than the X-Ray film.
    Agree with "only stop down as far as necessary to ensure efficient focus", but since I'm contact printing the film, I like to stop down even further to cover any focusing error on my part.
    Greg
    Then you should be good to go.

    I own a depth gage and determined that 4x5 is where I draw the line with my capabilities and this tool. My rudimentary attempt at addressing this issue quickly convinced me with the broad dimensions involved I needed to seek an expert machinist. Since I had one in our local LF photo group who was able to assemble a test jig for the task at hand, it was an easy fix.

    For the purposes of this thread and other interested in this subject within the archival record, a last check would be to take playing cards and spring cloths pins and grip the cards so that they are standing on edge vertically and place them on a 45 degree diagonal one a table top at small increments distance increments and after properly squaring up the standards make a photograph wide open on the center card in the array and process and proof the result. That will pretty much let you know all you need to know about the variables involved. I just like to know that when the price of sheet film in larger formats is as pricey as it is, I can make any image confident that if it looked sharp on the GG and I wanted to go no further down the F stop scale than f22 then I would not hesitate to do so. Any format can be evaluated with this last check, but the smaller the format the closer the tolerances of the cards should be. If you are a real math person, you could actually do a circle of confusion computation for the specifics in your set up and adjust in a specific way how you would complete the test and view the results.

    Time to get out and make some 11x14 photographs!

  6. #6

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    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    I recall a procedure for checking focus shift (effective focal length changing with aperture) that was simple and potentially very precise: place a ruler at a very slight angle to the film plane, and focus on a selected graduation near the center of the frame; make one exposure wide open and one at a small aperture, and after development see which graduation is sharpest. If it is not the selected one, then the groundglass and/or filmholder are out of tolerance; if the small aperture image is sharpest at a mark different from the wide-open one, the lens has focus shift.

    Without the right tools, measuring less than the machinist's "half thousandth (0.0005 inch)" is not simple. On the other hand, if a twelve-inch ruler is graduated in sixteenths of an inch, and rotated so the ends are 1/16 inch away from parallel to the film plane, the 1/16 inch markings each represent a depth change of about 0.00065 inch which ought to be close enough. (Bear in mind that the face of the ruler has to be reasonably straight.)

    My apologies for the Anglo-centricity of this description; in metric, rotating a 30 cm scale so that the ends are 1.6 mm out of plane will do the same job

  7. #7

    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Quote Originally Posted by Harold_4074 View Post
    I recall a procedure for checking focus shift (effective focal length changing with aperture) that was simple and potentially very precise: place a ruler at a very slight angle to the film plane, and focus on a selected graduation near the center of the frame; make one exposure wide open and one at a small aperture, and after development see which graduation is sharpest. If it is not the selected one, then the groundglass and/or filmholder are out of tolerance; if the small aperture image is sharpest at a mark different from the wide-open one, the lens has focus shift.

    Without the right tools, measuring less than the machinist's "half thousandth (0.0005 inch)" is not simple. On the other hand, if a twelve-inch ruler is graduated in sixteenths of an inch, and rotated so the ends are 1/16 inch away from parallel to the film plane, the 1/16 inch markings each represent a depth change of about 0.00065 inch which ought to be close enough. (Bear in mind that the face of the ruler has to be reasonably straight.)

    My apologies for the Anglo-centricity of this description; in metric, rotating a 30 cm scale so that the ends are 1.6 mm out of plane will do the same job
    I know that there are many ULF contact printers that have come to accept a lower bar of optical resolution because it is quick and easy. I know this because I was one of them. What cured me was an unwillingness to accept any degradation of print "snap" in what I have come to be familiar with in an 8x10 contact when the shift is made to a 11x14 or 8x20 contact print. What scared the HELL out of me on this issue was the lack of ANSI standards on formats beyond 8x10 and the myriad of manufacturers that produce holders for these formats without even a hint as to what is being produced? Call me high maintenance, but when I am paying $10 a sheet for film I believe in hedging my bets with the advice of specialized expertise. Of course YMMV.

  8. #8
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    Re: 11x14 Fidelity Medical Film Cassettes - film registration distance

    Quote Originally Posted by Michael Kadillak View Post
    What scared the HELL out of me on this issue was the lack of ANSI standards on formats beyond 8x10 and the myriad of manufacturers that produce holders for these formats without even a hint as to what is being produced?
    Just for the record, the ANSI standard does include specifications for 11x14 and 14x17, though not for other banquet/ULF sizes. Doesn't invalidate your concern, of course, given the evident variation in holder design and manufacture in these formats.

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