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Thread: Focus Calibration on Crown Graphic Special

  1. #1

    Focus Calibration on Crown Graphic Special

    Hi All! New user - fist post. I recently bought a beautiful Crown Graphic Special (SN#934971) with a 135mm Schneider-Kreuznach Xenar f/4.7 lens. I am planning on trying it out this Friday but would like to confirm my focus will be accurate before I go and shoot/process a bunch of film. I set it up on a tripod last night just to get a feel for things. What I found was that the "correct" focus point via the (top mount) rangefinder was different than the focus point determined when using the ground glass. I had a look at the RF mechanism to see if the proper cam was installed but couldn't see and stamped numbers on the cam. I have no reason to suspect it was changed out but wanted to check anyway. I then moved onto the GG and found that it had the ground glass with a Fresnel in front. These were both installed correctly. From what I have read online, it seems like all CG Special versions came from the factory with a Fresnel installed. I would like to confirm this somehow. I read that the height of the "bosses" would be a good indicator but I don't know what a boss is. The stacked GG and Fresnel sit just a bit higher than the two small rectangular pieces which sit on each side of the glass. These two pieces would be the same ones which the metal retainer clips screw into. The stacked GG and Fresnel sit flush with the four raised corner "posts" in the outer corners of the general opening. I hope this makes sense. If the Fresnel was never supposed to be there, I will just remove it. I could shoot some test shots but would prefer to not waste any film... Any help would be appreciated!
    Attached Thumbnails Attached Thumbnails 20180515_202239.jpg   20180515_202258.jpg  

  2. #2

    Join Date
    Sep 2010
    Posts
    442

    Re: Focus Calibration on Crown Graphic Special

    The Fresnel is supposed to be there and incorrect placement can throw focus off. The etched lens side faces the ground glass. There are any number of factors that could be throwing GG focus vs. RF off if the camera has been messed with. The screws holding the GG look like they have been removed by an NQP (non-qualified person) at one point, so who knows? If you can work it out you will have an excellent camera. PM me with your email and I will sent you a copy of the Graphic Repair Manual for the TRF.

  3. #3

    Join Date
    Sep 2003
    Location
    South of Rochester, NY
    Posts
    272

    Re: Focus Calibration on Crown Graphic Special

    If you have a dial (or digital, better) caliper, you can do a quick check.

    First, remove the graflock back focus panel and turn it over to view the inside. At the four corners are nice flat places to measure from that high spot down to the Fresnel. It should be .140 or very close to that. But you must be very careful to place the end of the caliper evenly on the flat high corner spot and hold it at 90 degrees! Measure several times at each corner until you get consistent results.

    If you want/need the manuals, they're available here:
    http://www.southbristolviews.com/pic...icmanuals.html

    Calibrating the top rangefinder is not much fun but not too difficult either. However, since you say there are no numbers on your cam, I would suggest borrowing or buying another cam before adjusting to that one. You really don't want your rangefinder adjusted to some home-made cam and have it out of adjustment to factory cams.

    Another thought... How did you place your front standard? If you have stops, they may be in the wrong place? If you don't have stops, that's another whole problem...


    Good luck with it!

  4. #4
    gimenosaiz's Avatar
    Join Date
    Jan 2015
    Location
    Spain
    Posts
    196

    Re: Focus Calibration on Crown Graphic Special

    Hi!

    I had focus issues with my Pacemaker.
    I finally discovered that the ground-glass was wrongly placed with the rough side pointed to the back instead to the lens. I comment this because I had the same doubts !!!
    I shot several sheets with my Optar 135/4.7 using the rangefinder and the GG. The GG images were out of focus while the RF were right. It was more evident when I shot my first photo with the Aeroektar.

    Good luck!
    Cheers
    Antonio

  5. #5

    Re: Focus Calibration on Crown Graphic Special

    Quote Originally Posted by Neal Chaves View Post
    The Fresnel is supposed to be there and incorrect placement can throw focus off. The etched lens side faces the ground glass. There are any number of factors that could be throwing GG focus vs. RF off if the camera has been messed with. The screws holding the GG look like they have been removed by an NQP (non-qualified person) at one point, so who knows? If you can work it out you will have an excellent camera. PM me with your email and I will sent you a copy of the Graphic Repair Manual for the TRF.
    Thanks! Will let you know.

  6. #6

    Re: Focus Calibration on Crown Graphic Special

    Quote Originally Posted by RichSBV View Post
    If you have a dial (or digital, better) caliper, you can do a quick check.

    First, remove the graflock back focus panel and turn it over to view the inside. At the four corners are nice flat places to measure from that high spot down to the Fresnel. It should be .140 or very close to that. But you must be very careful to place the end of the caliper evenly on the flat high corner spot and hold it at 90 degrees! Measure several times at each corner until you get consistent results.

    If you want/need the manuals, they're available here:
    http://www.southbristolviews.com/pic...icmanuals.html

    Calibrating the top rangefinder is not much fun but not too difficult either. However, since you say there are no numbers on your cam, I would suggest borrowing or buying another cam before adjusting to that one. You really don't want your rangefinder adjusted to some home-made cam and have it out of adjustment to factory cams.

    Another thought... How did you place your front standard? If you have stops, they may be in the wrong place? If you don't have stops, that's another whole problem...


    Good luck with it!
    Appreciate the information! Thanks.

  7. #7

    Re: Focus Calibration on Crown Graphic Special

    Quote Originally Posted by gimenosaiz View Post
    Hi!

    I had focus issues with my Pacemaker.
    I finally discovered that the ground-glass was wrongly placed with the rough side pointed to the back instead to the lens. I comment this because I had the same doubts !!!
    I shot several sheets with my Optar 135/4.7 using the rangefinder and the GG. The GG images were out of focus while the RF were right. It was more evident when I shot my first photo with the Aeroektar.

    Good luck!
    Cheers
    Antonio
    Thanks Antonio. Sounds like I need to do some testing.

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