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Thread: lefthand side of image unfocused/lense problem?

  1. #11

    Re: lefthand side of image unfocused/lense problem?

    A couple of questions that might help diagnose what's going on: Does the image get unsharp abruptly, or does it "fade" from sharp to fuzzy. Is the edge of the fuzzy area parallel with the edge of the film, or does it curve?

    You definitely can have a problem that's related to only one lens, though I'm having a hard time visualizing what sort of problem would lead to the effect that you're seeing. If the rear element of the lens doesn't protrude past the rear barrel, set the lens down on a table and check to make sure that everything that should be parallel with the table is parallel. This would include the lens board, the back and front of the shutter, and the top of the front lens barrel. If you're comfortable doing so, you might want to check the lens cells to make sure they're not cross-threaded in the shutter and that they're screwed all of the way in. (Just hand tight...they don't need to be screwed down hard.) Don't do any of this if you're not comfortable handling your lens these ways.

    You mentioned in your original post that the lens board can be moved "in line with the camera". By this, do you mean that you can move it in the same direction that the bellows fold up? If so, you might try folding up a bit of paper and sticking it in between whatever locking mechanism your camera uses for lens boards and the board itself. That should hold the lens board tight so that you can see if that's the problem.

    This is a stumper. I hope you figure it out soon...I'm sure it's frustrating.

  2. #12

    Join Date
    Nov 2008
    Posts
    3

    Re: lefthand side of image unfocused/lense problem?

    The edge of the soft focus area is parallel to the edge of the film and it starts quite abruptly.
    The lensboard moves up and down and left and right but can't be tilted. At one point I thought I might be moving the lensboard when using the cable release - but I guess that would blur the entire image, not just one part of it.

    I will go back to the repair shop tomorrow. I am happy that I am somewhat prepared now, as I thought it was a bit unconvincing to blame the problem on the image circle.

  3. #13
    Cooke, Heliar, Petzval...yeah
    Join Date
    May 2006
    Posts
    698

    Re: lefthand side of image unfocused/lense problem?

    Maybe lens fell during mounting on the ground and on of the glass elements chiped and created a blur on one side.
    Peter Hruby
    www.peterhruby.ca

  4. #14

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,868

    Re: lefthand side of image unfocused/lense problem?

    You can easily tell if there is a problem with the lens by rotating it on the board and shooting a test shot. If the soft area moves then there is a problem with the lens. If it stays in the same place then it is a problem with the board or the camera.

  5. #15

    Re: lefthand side of image unfocused/lense problem?

    A lot of good things to look at have been mentioned.

    I would check the lens retaining ring along with the pin (which looks like a tiny screw). I once screwed my lens retaining ring in backwards. Because of this, the ring did not extend through the hole in the lens board, the result was that that the lens was a little loose on the lensboard and the lens was at a slight off angle to the lensboard.

  6. #16

    Join Date
    Nov 2003
    Posts
    1,217

    Re: lefthand side of image unfocused/lense problem?

    When I got my f/4.5 75 mm Rodenstock, I noticed something similar, which I had not seen before, even with my f/6.8 90 mm lens. It turned out to be due to poor alignment of the standards. As others have mentioned, alignment may be more crucial for wide angle lenses, particularly if you focus at roughly the same subject distance. For example, for the same inadvertent tilt, at the same subject distance, the angle the exact subject plane makes with the vertical is twice as great with a 75 mm lens as it would be with a 150 mm lens.

    Alignment problems could arise either because the lens is mounted with a slight tilt or swing, most likely because of the pin, or because the standards are out of alignment.

    Here is one way to test the alignment of the standards. Point the camera down so it is plumb and one of the standards is level in all directions. For example, you can use a small level on the ground glass. Then test to see if the other standard is also level. If the geometry of your camera allows it, you may also use a dial caliper to measure the distances between the standards at the four corners to see if they differ. Neither of these methods will guarantee exact alignment, but you should be able to reduce the angle between the standards to less than a quarter of a degree.

    The f/4.5 75 mm Grandagon has an image circle (when focused at infinity) of 195 mm, and it would be larger for close subjects. That should allow shifts/rise/fall of 24 - 28 mm, depending on the orientation of the frame. I use mine regularly with such shifts. Of course, there is reduction in intensity, and sometimes it is hard to distinguish that from loss of sharpness. But when used with a center filter, I don't see any obvious loss in sharpness at the corners.

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