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Thread: 8x20 light leaks?

  1. #1

    Join Date
    Jul 2010
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    8x20 light leaks?

    hi

    I have 8x20 film holder which I loaded both sides today using Foma ISO400 film (actually is 2 sheets of 8x10 per side). The first side is exposed at 1/60 at f22 and developed at HC110 Dilution B for 7 minutes. It turned out well.

    The 2nd side of the film is also exposed at 1/60 at f22 (same scene as the 1st one so no change in exposure)and developed in the same manner but it turned out all black (overexposed) with no details at all. The only thing i did differently from the 1st exposure was that I removed the dark slide from the film holder and waited for a few minutes before tripping the shutter. I was walking for someone to walk into the frame I composed.

    Would this few minutes of removing the darkslide caused the overexposure? I did covered the dark slide opening with my dark cloth.

    I just checked the camera and film holder for light leaks using a torchlight in a darkened room. There is just some light leaks at the lensboard top edge but no signs of light leaks at the dark slide opening or bellows. I would expect such light leaks to cause some streaks or uneven exposure but not overall overexposure.

    I would do a test tomorrow by shooting immediately after removing the dark slide. However if you have other suggestions, I would be glad to hear them.

  2. #2

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    Re: 8x20 light leaks?

    I'd load it with two sheets of 8x10 paper, it's a lot cheaper than with film for the light leak tests!

  3. #3

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    Re: 8x20 light leaks?

    "I just checked the camera and film holder for light leaks using a torchlight in a darkened room. There is just some light leaks at the lensboard top edge but no signs of light leaks at the dark slide opening or bellows. I would expect such light leaks to cause some streaks or uneven exposure but not overall overexposure".

    Any light leak will have an effect on the negative. The one at the lensboard could well be the problem. Also your film holder probably leaks through the slot for the dark slide. This may not be noticed when the exposure is made immediately,but he wait time exacerbates the situation. Do you leave the darkcloth over the camera during all exposures? you should as this eliminates many undetectable light leaks.

  4. #4

    Re: 8x20 light leaks?

    Ah yes, welcome to the world of ULF where the the remarkable properties of light will search out and publicize each and every weakness in the integrity of the camera/film holders/exposure process. Light leaks tortured me for six months or more before I finally got the situation under control. It is my experience that I rarely had a whole sheet of film overexposed although I could see in your situation how it could happen. The norm for me was to see a section of the film dark and that was an excellent clue as to the "why". I will share with you that each side of the holder is uniquely independent in its issues of integrity and need to be address on its own. That being said it is entirely possible that your at question side of the holder may have been compromised before you put it in the camera. Here are the things I did to get my holders and camera in check. This is just my protocol, nothing more. YMMV.

    Use the same maker of holders and ensure the T distance of each holder is checked and consistent.
    Unscrew the top flap plate on each side of the holder and make sure the black felt is covering the metal light flap and that the flap is fully extended to prevent light leaks. I painted all of the interior components of my 8x20 film holders under the dark slide a flat black all the way up to and beyond the light traps to include the side of the holders. Always carry the loaded film holder in a light proof septum and put it back after the exposure ASAP. Always keep a dark cloth over the back of the camera when making an exposure. Place black fibre tape over the seams of the flap section of the holder when film is loaded. Reverse bend the dark slides should they exhibit curve. They will straighten out as a function of time. Eventually you will excise all of the light leak demons and all will be well.
    Last edited by Michael Kadillak; 11-Mar-2017 at 20:27. Reason: typo

  5. #5

    Join Date
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    769

    Re: 8x20 light leaks?

    Some additional things to keep an eye on.

    1) A pinhole at the lensboard can act - well, like a pinhole. Short exposures can sometimes result in what looks like movement or a double image - long exposures might result in gross overexposure.

    2) Check your filmholders for squareness. This is less of a problem with smaller formats. ULF, especially the long, skinny 8x20 and other panaromic formats can sometimes have filmholders that are out of square. The filmholders are made of wood and wood moves - it bends, warps. I had a couple of holders that I was getting light leaks from - eventually, I laid a straightedge across the length of the holder and found that it had curved a significant amount along the length - so the long ends (along the 20" sides) had warped into a slight bow shape. The springs on the filmholder frame of the camera were not strong enough to push the wood back into shape i.e. flat, and as a result I was getting light leaks.

    Good luck. Cheers, DJ

  6. #6

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    Re: 8x20 light leaks?

    thanks all for the useful tips on preventing light leaks. I think i found the issue and unfortunately it was my own undoing. When the film holders came to me ,one of the the darkslide disintegrated and I DIY one with black acrylic. Today I realised the 2 mm thick acrylic is not light proof. I place 8x20 photo paper on each side of the film holder and placed the film holder under light for half an hour. The side with the acrylic darkslide was fogged when I developed the papers.

    Let me look for alternative dark slide materials and try again. Again, the tips given are excellent and I will use them when I use my other holder.

  7. #7

    Re: 8x20 light leaks?

    Quote Originally Posted by pound View Post
    thanks all for the useful tips on preventing light leaks. I think i found the issue and unfortunately it was my own undoing. When the film holders came to me ,one of the the darkslide disintegrated and I DIY one with black acrylic. Today I realised the 2 mm thick acrylic is not light proof. I place 8x20 photo paper on each side of the film holder and placed the film holder under light for half an hour. The side with the acrylic darkslide was fogged when I developed the papers.

    Let me look for alternative dark slide materials and try again. Again, the tips given are excellent and I will use them when I use my other holder.
    Glad to hear you identified the issue as I suspected as I have never had a whole sheet of film exposed in a holder.

    Sandy King (one part of S&S Film Holders) has considerable experience in this arena as does Richard Ritter. Both have always been very gracious on sharing their knowledge base to fellow LF/ULF photographers.

  8. #8

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    Re: 8x20 light leaks?

    Quote Originally Posted by Michael Kadillak View Post
    Glad to hear you identified the issue as I suspected as I have never had a whole sheet of film exposed in a holder.

    Sandy King (one part of S&S Film Holders) has considerable experience in this arena as does Richard Ritter. Both have always been very gracious on sharing their knowledge base to fellow LF/ULF photographers.
    Thanks Michael. Your comment about it being overexposed even being before putting in the camera got me thinking.


    Sent from my Redmi Note 3 using Tapatalk

  9. #9

    Re: 8x20 light leaks?

    Quote Originally Posted by pound View Post
    Thanks Michael. Your comment about it being overexposed even being before putting in the camera got me thinking.


    Sent from my Redmi Note 3 using Tapatalk
    Great!

    I hope you get this issue resolved and become a dedicated 8x20 shooter. It truly is a fabulous format and a truly differentiating visual tool as many others have discovered.

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