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Thread: Disastrous Consequences (solved: fog with Intrepid lensboard)

  1. #11

    Join Date
    Apr 2020
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    13

    Re: Disasterous Consequences

    I should add that in the field I discovered the rear element and lensboard were loose, but I thought I took care of it (without tools)

  2. #12
    Foamer
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    Oct 2010
    Location
    South Dakota
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    Re: Disasterous Consequences

    It's a good wide angle lens. Note the gap between the rear of the shutter and the lens board. I'm suspecting there is a light leak around the shutter as Jody suggested.


    Kent in SD
    Qui sedes ad dexteram Patris,
    miserere nobis.

  3. #13

    Join Date
    Apr 2020
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    13

    Re: Disasterous Consequences

    No, but the perimeter of the image on the ground glass was dimmer as I don't have a fresnel lens - yet.

  4. #14

    Join Date
    Apr 2020
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    13

    Re: Disasterous Consequences

    Here's a close up of the lens elements and the lens board contacts. Click image for larger version. 

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  5. #15

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    California
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    Re: Disasterous Consequences

    It appears the rear element may not be screwed completely into the shutter.

  6. #16
    Nodda Duma's Avatar
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    Nov 2014
    Location
    Brookline, NH
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    961

    Re: Disasterous Consequences

    Someone posted the exact same problem either here or on photrio a few months ago. The cause were the Intrepid lens boards: Thry may look opaque but they are not! They do not block the full spectrum.

    You can see an image in the center and the periphery is overexposed.

    Put your lens on a different lensboard and it will be fine.
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  7. #17

    Join Date
    Jan 2019
    Posts
    320

    Re: Disasterous Consequences

    Quote Originally Posted by Nodda Duma View Post
    Someone posted the exact same problem either here or on photrio a few months ago. The cause were the Intrepid lens boards: Thry may look opaque but they are not! They do not block the full spectrum.

    You can see an image in the center and the periphery is overexposed.

    Put your lens on a different lensboard and it will be fine.
    They’re not aluminum????

  8. #18
    Foamer
    Join Date
    Oct 2010
    Location
    South Dakota
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    2,143

    Re: Disasterous Consequences

    Quote Originally Posted by Nodda Duma View Post
    Someone posted the exact same problem either here or on photrio a few months ago. The cause were the Intrepid lens boards: Thry may look opaque but they are not! They do not block the full spectrum.

    You can see an image in the center and the periphery is overexposed.

    Put your lens on a different lensboard and it will be fine.
    WOW! Never would have guessed that but looking at the images that looks correct. The rear bell of the lens was shading the negative.


    Kent in SD
    Qui sedes ad dexteram Patris,
    miserere nobis.

  9. #19

    Join Date
    Apr 2020
    Posts
    13

    Re: Disasterous Consequences

    This picture shows a gap between the locking nut and the lens board. I dismantled and found that it didn't quite fit into the hole. So I enlarged the hole and now the nut goes right up against the lens board. Could that have caused such a problem? I can't figure how. I guess now I need to make some test exposures with this adjustment.

  10. #20

    Join Date
    Jan 2019
    Posts
    196

    Re: Disasterous Consequences

    Quote Originally Posted by brianentz View Post
    Here's a close up of the lens elements and the lens board contacts. Click image for larger version. 

Name:	IMG_3282.jpg 
Views:	93 
Size:	39.6 KB 
ID:	208378Click image for larger version. 

Name:	IMG_3283.jpg 
Views:	48 
Size:	51.7 KB 
ID:	208379Click image for larger version. 

Name:	IMG_3282.jpg 
Views:	93 
Size:	39.6 KB 
ID:	208378Click image for larger version. 

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Views:	46 
Size:	49.5 KB 
ID:	208381
    Picture 4 here shows the retaining ring not fully seated into the lens board. When this happens, the rear element may also not be fully screwed into the back of the shutter, and there could be light leaks around the lensboard hole.

    As a quick and dirty check on whether the lensboard is not fully opaque and that could also be causing problems, you could try lining the back of the lensboard with something opaque, even aluminum foil (not ideal because it's shiny, but ok for a test).

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