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  1. #1
    mr rusty's Avatar
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    Correcting convergence

    I have an enlarger where I can swing the whole head, which in theory I guess I can use to correct convergence in shots of buildings. I haven't tried this yet, but obviously the focus will get mucked up a bit between the near and far points on the image from the enlarger lens. What are peoples thoughts? is this practical? or is the depth of field of the image never good enough for it to really work?

  2. #2
    Steve Smith's Avatar
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    There is a lot more depth of focus at the paper than there is depth of field at the negative so you might get away with just tilting the easel.

    If you can arrange it so that the planes of the negative, lens and paper all converge to the same point, the focus should be correct at all points (I think).

    http://www.ephotozine.com/article/co...-enlarger-4672


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  3. #3
    mr rusty's Avatar
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    Thanks Steve! I do have a tilting lens board as well, so in due course I will try this. Thanks for the article link which answers all the questions.

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    I have made slight corrections by tilting the easel. Stop down and make test prints to see if burning or dodging part of the print is needed. Don't try to do too much. You didn't mention the size of the negative which might make a difference.

    http://www.jeffreyglasser.com/

  5. #5
    MattKing's Avatar
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    Always remember that when you do this to modify the shapes of things like buildings, you will also be modifying the shapes of everything else in the scene.

    People, cars and signs can look really strange when they are "modified for convergence".
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  6. #6
    ic-racer's Avatar
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    Correcting convergence with the enlarger has some advantages over front rise.
    1) You use the center of the taking lens
    2) The actual angle of view is greater when pointing up, compared to a front rise
    3) You can use smaller, more compact, more inexpensive lenses.

    Pictures show:
    1) a modest Durst enlarger that does a correct baseboard tilt and lens tilt.
    2) Durst 8x10 enlarger, again with baseboard and lensboard tilt.
    3) my Durst used to make the following picture
    4) 8x10 negative from a lowly Symmar-S 210mm pointed up. Notice that there is no light falloff at the top of the image, as one would get with a wide field lens with a lot of front rise.




    Last edited by ic-racer; 03-05-2012 at 02:38 PM. Click to view previous post history.

  7. #7
    ic-racer's Avatar
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    Quote Originally Posted by MattKing View Post
    Always remember that when you do this to modify the shapes of things like buildings, you will also be modifying the shapes of everything else in the scene.

    People, cars and signs can look really strange when they are "modified for convergence".
    I guess it is in the eye of the beholder. I find uncorrected leaning signs, people, wine-bottles and cars odd, unless you want the special effect.

    Attached image (from http://images.nikonians.org) showing pretty normal-looking people, signs and cars in a highly corrected image.
    Click image for larger version. 

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    Last edited by ic-racer; 03-05-2012 at 02:59 PM. Click to view previous post history.

  8. #8
    David A. Goldfarb's Avatar
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    Quote Originally Posted by ic-racer View Post
    Correcting convergence with the enlarger has some advantages over front rise.

    3) my Durst used to make the following picture
    4) 8x10 negative from a lowly Symmar-S 210mm pointed up. Notice that there is no light falloff at the top of the image, as one would get with a wide field lens with a lot of front rise.


    Nice demo!
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  9. #9
    mr rusty's Avatar
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    I knew all the old hands would have all the answers! This forum is great. For those who have read my other posts, I am in the process of setting up a dark room. Until very recently I had never made a print before in my life - so it's all one huge learning curve. The darkroom is nearly finished - I ordered some epoxy for the sink today. I still haven't ever developed a film (only prints so far from existing negs), but my supplies from silverprint came yesterday so it won't be long. My family think I am slightly mad investing in something which most people think is obsolete!



 

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