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Thread: Lens Convergence?

  1. #11
    Stefan
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    Re: Lens Convergence?

    Not only the best solution, it is also the only solution for getting a negative without vertical convergence. The 90mm Angulon does give a fair bit of rise at F32 with corner sharpness suffering, although I agree a Super Angulon, or one of the similar lenses from competitors, would be a much better bet for taking pictures like the second one posted.

  2. #12
    multiplex
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    Re: Lens Convergence?

    ...

  3. #13
    Cordless Bungee Jumper Sirius Glass's Avatar
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    Re: Lens Convergence?

    Next time I will shoot several different variations of a building. Obviously, doing it correctly with one photograph the first time out using rise is a bit ambitious.

    Steve
    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  4. #14

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    Re: Lens Convergence?

    Quote Originally Posted by Sirius Glass View Post
    Next time I will shoot several different variations of a building. Obviously, doing it correctly with one photograph the first time out using rise is a bit ambitious.
    It's not about the number of shots. It's about the precision of your work. Learn to use a level the way engl described:

    Quote Originally Posted by engl View Post
    Correcting for convergence is easy. Use a level to make sure your camera back standard is level (left to right) and perfectly vertical (front to back). That is all you need to make sure that lines that are vertical in the real world will be vertical in your photo.
    I use one of those hot shoe bubble spirit levels, I always have it in my pocket. I put it against the ground glass, against the lens board, on top of the ground glass frame. Never rely on levels elsewhere on the camera or the tripod. There is enough that can go wrong within the camera's structure.

    After the camera is level, I use the front rise to control the composition.

    Good luck!

    Michael

  5. #15
    Deardorff Sales and service
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    Re: Lens Convergence?

    I'm not sure where I posted this question: "Do you always use your cameras swings and tilts?" . It seems here that they were needed. Now is it a "natural thing to do". Meaning, when you set up your camera do you automaticaly square the back to your subject? You really should. I've been to Harpers Ferry many times and it is nearly impossable to find a level surface untill you look at the roof lines, window sills, edges of buildings, some of the phone poles...See what I mean? I had a nice yearly job taking pictures of Toll road payment booths. I could do it without stopping traffic and not show a single car. (use two #4 neutral density filters and really long exposures)
    I'd be up on a hillside looking down (camera movement term) Square up on a light pole rear swing as needed and front movements to pull the plane of foci. This should become second nature!! Good luck next time.


    Quote Originally Posted by Sirius Glass View Post
    These are two photographs that I took learning to correct for convergence. The negatives were quickly flat scanned saved; then GIMP was used to reverse the images and adjust the contrast so that they would be viewable.

    Both negatives were taken with a Schneider-Kreuznech Angulon f6.8 90mm lens. In both photographs I thought that I had corrected for convergence, but on the right of both of them there is convergence. The one of Haper's Ferry has slight convergence and the one of the church has a larger convergence.

    Are the convergences an artifact of the lens or an Operator Assisted Failure [OAF]?

    Steve
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  6. #16

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    Re: Lens Convergence?

    Quote Originally Posted by Sirius Glass View Post
    Next time I will shoot several different variations of a building. Obviously, doing it correctly with one photograph the first time out using rise is a bit ambitious.

    Steve
    Not at all ambitious. Use the grid on the ground glass and you cannot go wrong. Levels are good, but what if your subject is square but not perfectly level and/or plumb??

    The GG shows you precisely what you will get on the negative.
    One man's Mede is another man's Persian.

  7. #17
    Unwitting Thread Killer Ari's Avatar
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    Re: Lens Convergence?

    I've been struggling with this lately...
    http://www.largeformatphotography.in...ad.php?t=78766

    A level helps get you in the ballpark, but adjusting the back, with the gridded screen, is the final say.
    Being low to a building makes things more difficult to square up as well.

  8. #18
    multiplex
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    Re: Lens Convergence?

    steve,

    get a post level ... they cost less than 1$.
    keep it in your pocket, and put it on the center of
    your camera's box when you set it up.


    you won't have trouble with converging lines as long as the bubble
    shows you the back is level. if you turn the camera just make sure you
    check the bubble again.

    make a grid on your computer or download one, and go to a copy store
    and have them print it on clear acetate, and just slide it on top of your ground glass.
    you don't need anything fancy, and you don't need to mark your glass with pencil &C.

    you will be able to SEE everything is straight up + down with the grid,
    and if you want keystoning, you will be able to see that too ...

    if you like photographing buildings, you might consider getting a view/ field camera
    that allows you to adjust the film plane after you tilt the camera...


    good luck !
    john

  9. #19
    Cordless Bungee Jumper Sirius Glass's Avatar
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    Re: Lens Convergence?

    I have a six inch spirit level that is in the camera bag when I go out shooting. The best place to set up the camera for the church picture was lower down than the base of the church. I thought that I had corrected the camera position with the rise. If I had the back of the camera vertical then I would not have had enough rise to get the top of the tower.
    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  10. #20
    Kirk Gittings's Avatar
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    Re: Lens Convergence?

    Schneider-Kreuznech Angulon f6.8 90mm lens
    If I had the back of the camera vertical then I would not have had enough rise to get the top of the tower.
    That lens IME does not have a large enough image circle to properly shoot architeture.
    Thanks,
    Kirk

    at age 73:
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

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