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Light Leak? on Pacemaker 45

 
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rsdean



Joined: 27 Jun 2002
Posts: 52
Location: NE Maryland

PostPosted: Tue Nov 12, 2002 12:30 pm    Post subject: Reply with quote

I developed a tank of negatives the other night and found that I had several (why not all?) with what looks like a very minor light leak along the lower edge (in camera position) of the negative--like someone put a greasy hand on the film, as there are four patches about the size of fingerprints. At least two negatives on which this is clear show identical patters. I had thought that this was a problem with light leaks in the processing tank on a previous batch, but I took extra precautions on this batch--and with it being identical on multiple sheets I must conclude that it's a problem with the camera. I've gone over the camera and tightened up the screws holding on the spring back, and also the screws holding the back to the body. Perhaps this latter was it--there was room to tighten them, and with three screws a four patch leak would seem plausible. Any other ideas or suggestions? I'd like to patch this before exposing any more film...

Since the film isn't completely blackened the leak is obviously extremely faint.

Rob Dean

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alecj



Joined: 09 May 2001
Posts: 853
Location: Alabama

PostPosted: Tue Nov 12, 2002 1:08 pm    Post subject: Reply with quote

Once you are absolutely sure its the top, or bottom of the film back, sounds like you're ready to spend quality time with your camera, and a flashlight, in some dark, intimate place. There are so many possibilities you've just got to rule thme out one at a time.
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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Wed Nov 13, 2002 1:20 am    Post subject: Reply with quote

I have had good luck focusing a mini mag flashlight to spot at 1 to 2 inches and putting it inside the camera and observing the exterior in film handling conditions to show up leaks with and without film holders installed. To test if they are fixed I use 400 speed and push 1 stop if needed.
Charles

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rsdean



Joined: 27 Jun 2002
Posts: 52
Location: NE Maryland

PostPosted: Wed Nov 13, 2002 12:05 pm    Post subject: Reply with quote

I went over the camera with a mini maglite last night and couldn't find any leaks. I put it inside to check the bellows, checked the lensboard from both sides, took the lensboard off and put in a film holder and ran the light all around the edges while staring down the bellows. I didn't find anything visible, except with the bad film holder, which has clearly lost its light seal at the darkslide end. More powerful flashlight? I've been using 400 film--and will take the camera out in the light and develop a blank to see what there is to see.

Rob Dean

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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Wed Nov 13, 2002 8:18 pm    Post subject: Reply with quote

I put the flashlight Inside and view from the Outside. Also varry the angle. Some put a 40 clear appliance bulb in a hand held socket but one must be careful not to let the HOT bulb touch anything.
Charles

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rsdean



Joined: 27 Jun 2002
Posts: 52
Location: NE Maryland

PostPosted: Fri Nov 15, 2002 3:50 am    Post subject: Reply with quote

I had the time to check again tonight, and tried putting the flashlight inside. The good news is that the bellows is apparently light tight, but I can see a faint line of light above and below the film holder when it is in place. Would this be enough to be a problem? If so (and I don't see anything else that would be a clue) does anyone have any suggestions for how to tighten up the fit of the holders on a spring back? (Or maybe improvise some curtains at the top and bottom of the glass shield?)

Rob Dean




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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Fri Nov 15, 2002 3:56 am    Post subject: Reply with quote

With older camera I usually just cover the back with the focusing cloth, which you probably don't have because you use the ground glass shade.
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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Fri Nov 15, 2002 6:43 am    Post subject: Reply with quote

Congratulations you've found the cause! Your springs are weak and not holding the film holder tight enough.
Try reforming the existing springs to increase pressure on the film holder, find spring stock and make new springs, or get some self adhesive black felt from a hobby shop and put a strip along the edges of the back where the light comes through.
Spring pressure should be 15 to 25 pounds pull. Yours are around 12 to 14.
Charles

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alecj



Joined: 09 May 2001
Posts: 853
Location: Alabama

PostPosted: Fri Nov 15, 2002 3:17 pm    Post subject: Reply with quote

I would add one caution - if you go the black felt route, don't alter the film plane position of the holder if you can help it. Otherwise, you'll have to reset your rangefinder.
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rsdean



Joined: 27 Jun 2002
Posts: 52
Location: NE Maryland

PostPosted: Fri Nov 15, 2002 10:28 pm    Post subject: Reply with quote

Les: True, I do not have a focussing cloth. Any suggestions on a commercial product?

As far as the felt goes, I am understanding this suggestion to be one of putting the felt on the outside of the camera over the cracks, rather than one of using the felt as a gasket material. Did I get that correctly? I thought about using something like teflon tape for gasketing, but that would bring in a whole bunch of issues about how to attach it and whether the film holders would slide over it.

Rob Dean

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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Sat Nov 16, 2002 4:18 am    Post subject: Reply with quote

The felt trick is the last on the list a it is just a stop gap measure, not a perminate fix. The felt, 1/16 inch thick, would be attached to the back around the film/ground glass opening. I would not put any on the notched edge on the dark slide side.
You stated ealier that this is a spring back, therefore the groundglass plate should have a pin protruding at each corner that the springs attach to and the springs each have a hole or holes about their center that screws attach them to the camera back; correct? If so they (the springs) have gentle curves from center to edge or they have formed angular turns, by taking the springs off, and reworking (reforming) the curviature or angular turns so that the springs put more pressure on the film holder would be the way to go. If preforming this procedure in such a way as to render the springs unuseable then the term would be BENDT out of shape!
Charles

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[ This Message was edited by: 45PSS on 2002-11-15 20:36 ]
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clnfrd



Joined: 26 Mar 2002
Posts: 616
Location: Western Kentucky Lakes Area

PostPosted: Sat Nov 16, 2002 1:30 pm    Post subject: Reply with quote

Also read "strange light leak"...this forum..2002-10-25. Fred.
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rsdean



Joined: 27 Jun 2002
Posts: 52
Location: NE Maryland

PostPosted: Fri Nov 22, 2002 4:08 am    Post subject: Reply with quote

Thanks for all the help, gentlemen. I took the camera out for a walk yesterday with an improvised cloth made from a couple of yards of black velveteen, and I hope to develop those negatives over the weekend and see if that helped. It's cumbersome to use, but was the easiest solution to test implementation of, so I'm trying it first. It does mean no handheld shots, though, so is unlikely to be the permanent sole solution. More later...

Rob Dean

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