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05-11-2013, 06:45 PM   #1
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Diagnosing light leaks

Tried to search for this, so pardons if I missed an obvious thread/website that deals with this.

I'm getting an intermittent light leak on my LX. It happens with both the pentaprism and the waist level finders. The light seals in the back seem okay to these newb eyes. The mirror bumper does not look to be deteriorating (the body was said by the seller to have been recently CLA'd by Eric), but it kind of looks to me like it is too far up, if that makes sense. The mirror does contact the foam when raised, but I just don't know how much the foam should be compressed by the mirror.

Below are two sample photos showing the problem. Do any practiced eyes out there have any tips? I was going to just order a foam seal kit from Jon Goodman, but he says he doesn't have LX kits. Anyway, thanks to any who are willing to help!

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05-11-2013, 07:58 PM - 1 Like   #2
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Have a look at the negatives... is the leak beyond the frame of the shot and extends to the sprocket holes? This will help to determine if the leak is related to the shutter sided or the film door.
05-11-2013, 09:09 PM   #3
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Checked the negs...the leak goes to the edge of the film, and appears to be strongest there. As I examine the negatives, sometimes the edge by the sprocket holes is burned, but it doesn't extend down to the image.

So if I'm hearing you right, if the leak goes to the edge of the film (which is not exposed by the shutter), then it should (must?) be on the door side? Also, the leak is generally strongest at the top of the image. IIRC, the image is inverted, so that means the leak would probably be at the bottom of the film door?

Thanks so much for your guidance! Looking at the negatives seems so obvious now...
05-12-2013, 10:44 AM   #4
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QuoteOriginally posted by filoxophy Quote
Also, the leak is generally strongest at the top of the image
Yep, you seemed to have nailed it...! It could be either at the edge prior to slipping under the pressure plate or leaving the pressure plate as the domain of the pressure plate forms a seal area around the film. Commonly, the hindge area is a source of the leak. If the light leaked look oddly patterned as if intermittent then the leak source may be the door latch side.

05-12-2013, 09:17 PM   #5
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Time often is a factor in the strength of the burn on the film: if you shoot and wind on quickly, you don't give the film much exposure time to the leak. But if you leave the camera in the light without advancing the film, you give more time for the leak to make a stronger exposure in one spot. You may be able to determine where the leak is coming from by shooting and advancing two or three times quickly, then leaving the camera in a bright spot for a longer time, then shooting two or three more quickly. If you know which frame was behind the lens during the pause, then you'll be able to see whether the leak is more toward the hinge or the latch.

My guess is that the leak is in the hinge end, and it's burning the last-shot frame after you wind on.
05-14-2013, 02:53 PM   #6
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QuoteOriginally posted by MysteryOnion Quote
It could be either at the edge prior to slipping under the pressure plate or leaving the pressure plate as the domain of the pressure plate forms a seal area around the film. Commonly, the hindge area is a source of the leak
...or it may have happened after the film was removed from the camera...


Steve
05-14-2013, 03:00 PM   #7
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QuoteOriginally posted by stevebrot Quote
...or it may have happened after the film was removed from the camera...
Thats a good point... true, but that would first mean that the film easily back rolled from not being tightly wound after coming out of the camera. I have yet to see a P6x7, P67 or P67ii not snugly roll the film paper up.

In the analysis of the light marks, the tell tailed reflected backing paper marking did not transfer that I could see.
05-14-2013, 03:10 PM   #8
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QuoteOriginally posted by MysteryOnion Quote
tell tailed reflected backing paper
Ummm...backing paper?

The negatives were 35mm. I would suspect the culprit to be a mildly squished film cannister or perhaps someone fiddling with the felt light trap after it was removed from the camera.


Steve

05-14-2013, 03:23 PM   #9
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I used to diagnose light leaks with a tiny "grain-of-wheat" light bulb put in the film compartment and taking the camera into the darkroom. The wires where thin enough not to interfere with closing the door. You can use a small LED with thin gauge wire or even a small keychain LED flashlight.
05-15-2013, 08:06 AM   #10
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QuoteOriginally posted by stevebrot Quote
Ummm...backing paper?

The negatives were 35mm. I would suspect the culprit to be a mildly squished film cannister or perhaps someone fiddling with the felt light trap after it was removed from the camera.


Steve
Your right Steve... wrong post, but similar problem... Sorry filoxophy.
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