2-sided Film Holders - Help

Discussion in 'Large Format Cameras and Accessories' started by Fotoguy20d, May 8, 2009.

  1. Fotoguy20d

    Fotoguy20d Subscriber

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    Okay, what am I doing wrong? Same result with 2 different 2-sided holders, 4 frames, all with the same fogging along the edge. Am I pulling the dark slide too far?

    Thanks,
    Dan
     

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  2. jnanian

    jnanian Advertiser Advertiser

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    dan

    when you pull the darkslide out does it come out smoothly ?
    maybe light is leaking in as you pull the darkslide out ... and put it back in ...

    john
     
  3. archphoto

    archphoto Member

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    I don't think this is a light leak, otherwise the top would be a lot darker.

    Please keep in mind, that before exposing you have to pull the dark slide completely out, after exposure you turn the dark slide 180 degrees and put it back in, so you can see that that side of the film holder has been exposed.

    Peter
     
  4. Venchka

    Venchka Member

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    This is at the flap end. Bad hinge tape? Light coming in under the flap. It happens.

    Another possibility: holder not seated correctly in camera. There are grooves and ridges that have to lign up to make a light trap. One more (actually happened to me) : the width of my Zone VI camera back is wider than my Grafmatic. Regular holders work but the Grafmatic leaks along the long side.
     
  5. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    It looks like you have an area of underexposure, not a light leak, at the top of the frame, which would be the bottom of the camera. This might be caused by the bellows impinging on the image area, but there might be some light diffracting around the bellows to give you a partial image.

    Then on the right side of the frame it looks like you have a light leak that isn't in the filmholder, because the rebate of the film is clear, so maybe the filmholder isn't seated properly in the back, or the bellows isn't completely attached to the back of the camera, or the bellows has a light leak on that side.

    On the left side of the frame there is a light leak that does enter into the rebate of the film. It looks like this film may have been lightstruck on that side before or as it was loaded.
     
  6. Fotoguy20d

    Fotoguy20d Subscriber

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    David,

    I think you're right about the bellows impinging. As for the edges, I provided some mis-direction there. The original image was taken using a digicam with the negtive on a lightbox - there's some light-rolloff along the one edge. On the left edge of the photo shown, which is the end of travel for the Speed Graphic shutter (perhaps some more info would have helped you), which was set at 1/30, it hung up slightly so that edge was over-exposed. That problem does not repeat on the thin negatives which were shot at 1/100s. However, the bellows are there in all 4 frames. The lens, for completing the description of equipment, was a cdv/petzval, the testing of which was the purpose of this exercise - you can see the vignette in the corners.

    Thanks,
    Dan
     

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  7. Ian Grant

    Ian Grant Subscriber

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    Looks like fogging probably while loading the film into the dark-slides.

    Ian
     
  8. jnanian

    jnanian Advertiser Advertiser

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    on a speed graphic it does not seem usual
    for the bellows to be hanging down and obstructing
    the film. could there be something inside the camera that
    might be doing something similar ?
    does the camera have a graflock back, and if so, have you removed
    the back and looked inside the back of the camera to see
    if there might be something else going on ?

    john
     
  9. Fotoguy20d

    Fotoguy20d Subscriber

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    I don't think the film was fogged while loading - The dark area is virtually identical (depth and angle) on all 4 frames. The bellows aren't sagging (although the angle seems to match the shape of the bellows). There's nothing inside the camera. I'm wondering if there's some sort of reflection or strange light behavior going on inside the lens - it's the lens I asked about in this post. It's "press fit" into a black ABS plastic lensboard, threads out, and around 1/2" of lens back into the cavity - having said that, I just looked at the part of the lens inside the body - I wrapped black electrical tape around the first 1/4" or so but the rear edge is reasonably shiny brass. I see more electrical tape and another test in my future. I had tape sealed the hole in the underside of the lens body and saw no light leaks around the aperture, by the way.

    Dan
     
  10. jnanian

    jnanian Advertiser Advertiser

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    h dan

    could the light be leaking around the lensboard ?
    and does this sort of leak happen when you use
    a different lens+board?
    since film is kind of expensive,
    it might be fun+easy to make some quick and dirty
    paper negatives to try to pinpoint what might be going on.

    you can load paper in the holders and leave them in room/daylight
    to see if it is the holders leaking or see if it your loading technique
    (load paper in safelight to see what might be going on)
    try shooting the paper using aroundish asa 6 or 10 as a starting point
    and use both this fun lens with no tape around lensboard and with ..
    and then with an actual speed graphic board+regular lens ...

    i wish i had some other suggestions ...

    john
     
  11. rmolson

    rmolson Member

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    Paper negative test, great idea. Wish I had thought of that before I blew through a bunch of film looking for a light leak
    Years ago and I am dating my self there was a device to check flash snyc using paper .
     
  12. wclavey

    wclavey Member

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    It looks to me as if you might be grtting some reflection from the inside surface (facing the lens) of the back on which the ground glass or film holder rests, based on the over exposed strip on the left hand side of the positive image you posted above. I had a similar situation like that on a Crown Graphic as soon as I started using a lens that had more coverage than the original 135mm Optar. So I put self-adhesive black felt on the inside edges and flat surfaces of the back (not on the film holder side) to reduce any reflection of light coming from the lens that was not actually falling on the film and it went away.
     
  13. Andrew4x5

    Andrew4x5 Member

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    I've have similar effects on a number of occasions. I suspect it's because I've accidently pulled the film holder away from its seating when withdrawing or reinserting the dark slide. The severity of the the effect of the fault depends on how far the holder is pulled away, the position of the sun relative to the holder, etc.

    If my supposition is correct, there are two solutions - apart from being more careful. 1) Tighten the springs that hold the film holder in place. 2) Hold the ground glass/film holder/camera back assembly tight while withdrawing/reinserting the dark slide.
     
  14. Dave Dawson

    Dave Dawson Member

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    Take two sheets of fast film and load into a dds....Place into camera and remove the slide for a minuet (Do not open the shutter) replace slide and develop both.

    If you have a light leak on the camera there will be fogging on that neg....If the film has been fogged before loading this will show up on the neg where the slide hasn't been removed..........Sorted.

    Cheers Dave
     
  15. Fotoguy20d

    Fotoguy20d Subscriber

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    Thinking about this carefully, looking at the positive image, I come up with the following:

    The film was not fogged prior to going into the holders - the edges are black.
    The over-exposed strip on the left edge of the frame is due to the shutter hanging up at the end as it closed - this is only apparent in the 1/30s frame. In the faster shutter shots, the shutter didn't hang and no strip is visible.
    The under-exposed section on top, was actually on the bottom of the camera when exposing the film, so it can't be due to the bellows sagging, which I didn't see when I looked in the camera. Also, its not due to stray light reflections since then it would be over, not under exposed. Also, not due to a light leak in the camera (again, under-exposure, not over, not to mention how straight it is - otherwise it would appear as fog) The slight angle and straight edge of the area make me think this is a bellows shadow - I need to see how the bellows are sitting when compressed back enough to focus this shot. I was thinking perhaps it's at the back of the bellows at the bottom, but it doesn't seem likely. Maybe a fold closer to the front or in the middle is sagging down just enough (or was in this setup).

    Dan
     
  16. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Looks like the whole stack of film was fogged at the edges at some time in the past. There is fog all along the left edge of the negative, it is 'under' the shadow of the film guide and is heaviest at the extreme edge of the film. Try developing an unloaded/unexposed sheet and see if it exhibits edge fogging.