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View Full Version : Light leak - please help diagnose



Guy Tal
4-Jan-2004, 07:16
Folks,

Thanks for the very helpful information in my previous thread. I scanned a sample showing the light leak I described and was wondering if you could help me diagnose it. I did get a couple of good exposures from the same lens, which leads me to believe it may be a sporadic problem with the shutter not closing all the way. I tested the lens on 2 lensboards and it sits flush and light-tight so I'm pretty sure the leak is not between the lens and board or between the board and camera. The previous owner told me the lens was sitting idle for over 2 years so it's possible a CLA is in order.

Here's what it looks like:

http://www.scenicwild.com/npn/leak_sample.jpg

Thanks!
Guy

neil poulsen
4-Jan-2004, 07:40
What camera are you using? What was the approximate aperture for this photo? Are you using some sort of lens shade? What kind of shutter are you using?

There's a large volume of light reflecting off the sand. Do you experience the same problem in less contrasty circumstances?

Guy Tal
4-Jan-2004, 07:49
Camera: Wista VX (used with other lenses on the same trip with no problem)
Aperture: f/32, I believe
No lens shade, but the same leak appeared in other scenes with no direct light
Lens: Nikkor M 300/9
Shutter: Original Copal 1

Thanks!
Guy

N Dhananjay
4-Jan-2004, 08:02
Check the bellows for pinholes by taking the camera into a dark room, inserting a film holder in the back and inserting a flashlight through the front standard - any pinhole should be quite obvious. Remember to try extensive movements - some pinholes are often hidden by folds in the bellows and only reveal themselve when flexed. I've found preserving your dark vision makes it easier to spot the pinholes, so try to avoid shining the flashlight into your eye. Check the seating of the film holder in the back. You can also check the lensboard while you are at it by removing the film holder, placing lens on the front panel and shining the flashlight on it from the outside and looking through the back. But I doubt it is going to be there - pinholes near the lens area tend to form double images. If you look at the sample picture you have posted, the left hand and top sides look relatively free from flare. The flare light seems to start in the top left region towards the middle and sprays across the film area towards the bottom right. The flare seems highest in the top left region and seems lower as you move away from that region. This suggests that the flare light was close to the top left corner, hence the higher intensity of flare there and lower intensity a greater distance from it. If you can figure out the orientation of the film in the back (which you can from the notches), I would think that you are going to find the leak near the top left corner of the picture area close to the back standard. I'm assuming that this is not an issue of the film holder not sitting properly in the back through operator error. Cheers, DJ

Guy Tal
4-Jan-2004, 08:26
Thanks DJ! I just tried the light in the bellows thing and there are no visible leaks anywhere on the bellows.
Guy

Jan Nieuwenhuysen
4-Jan-2004, 08:42
I have had a light leak in my camera some years ago that produced a similar result. In my case it was a light leak between the bellows material and the metal frame that attaches the bellows to the rear standard. It took me quite some time to figure out that one of the screws in the bellows frame was broken and hence the cloth was no longer attached leak proof to the frame. The screw had of course not fallen out so it was not apparent at first sight... I suppose a leak between bellows frame and rear standard would also produce an effect like this.

I just compared your scan to one of the transparancies I saved and they look very much alike (the leak, not the scenery). I have no experience with the Wista camera, so I can't really tell if this could be what's causing your problem, but I think it's an idea to check your bellows and bellows attachment to the camera for a leak. Succes, Jan

Tracy Storer
4-Jan-2004, 08:42
Guy, DJ has the right idea....we also need to remember this is your 300mm, and Wistas with a not overly long bellows. When you checked the bellows, was it racked out to around 12"? I would further guess it IS a bellows leak, near the back of the bellows, on the lower right. (users right, looking at the back of the camera) Also check that the bellows isn't separating from the back when you rack out. Good luck, let us know,

Gary Meader
4-Jan-2004, 09:40
I'm a bit confused. Are we worried about the light, center part of the image, thinking it's a leak, or are we concerned with the darker, underexposed area toward the outer edges of the frame? To me, the outside looks like the bellows are interfering by sagging or something. At least the snow looks dark...the trees look a bit light on the inside, tho. And at 300mm it's easy to imagine. Guy, does that look like it could be the problem?

Guy Tal
4-Jan-2004, 10:01
Gary - that's an interesting point I haven't thought of, but I think the lighter part in the center is the problem since you can see some ghosting there and it's not evenly exposed (the upper right corner is brighter than the rest). The bellows was certainly not sagging. As someone mentioned, the Wista has a fairly short bellows and it was stretched out to capacity with the 300mm.
OK, I removed the bellows and found some separation between the leather and plastic frame holding it in one corner. I super-glued it and am about to venture out for a couple of test shots. I do hope that turns out to be the problem!
I'll report back when I pick up my film at the lab tomorrow.

Guy

Cesar Barreto
4-Jan-2004, 10:25
Guy,

As the flare shows a straight border, it looks like a shadow from the wood frame in contact with film-holder. Probably, if you insert it on place you may find a leak at bottom on the right side. Good luck!

Eric Wagner
4-Jan-2004, 11:01
I agree with DJ and Tracy. If you are patient and persistent, you ought to be able to spot the leak in the darkroom. If not, then you will have to test with film. Set the camera up in your backyard, pull the darkslide, wait five minutes and then replace the slide. Do the same with another film, except this time make an exposure. Then do the same with your dark cloth wrapped around the rear standard and the rear 2/3 of the bellows, and another with you dark cloth wrapped around the front standard (make a tunnel in front of the lens) and the front 2/3 of the bellows. By studying the developed films you ought to be able to zero in on where the leak is coming from.

John Cook
4-Jan-2004, 12:51
Several things can cause this. And I donít know all your circumstances.

But a common problem I and my fellow students had as LF beginners in school looked exactly like this and was caused by a very small light leak between the film holder and the camera back.

The light leak, in turn, was caused by the holder slightly separating from the camera back while tugging on a stubborn slide.

Three cures. First, wax the holder slides with automobile wax. After years of experimentation, I have come to prefer Meguiarís High Tech Wax 26.

Second, keep the focus cloth draped over the top of the camera in bright sun for extra protection.

Third, while removing (and inserting) the dark slide with the right hand, get in the habit of squeezing the ground glass frame and holder against the camera back with the left hand.

bob moulton
4-Jan-2004, 14:23
Guy;

Another testing possibility: Set camera up for image and then encircle bellows from lens standard to film plane in your darkcloth or something large enough and preferably dark enough to cover the whole bellows. Make your images. Then duplicate that procedure without the dark cloth wrap on another set of images. If the first two are ok and the latter are not at least you have a suspicion it is the bellows.

Another thought: How new are your film holders and dark slides? It is possible though I would not say probable that the slides leak light. Still another possibility. Check the room where you load film. (I assume you aren't using ready/quickloads.) If light gets in there could your problem.

If all your negs were loaded at the same time that solution seems less possible, but hey!

You might open your film box, set a couple of sheets out, let them set in the dark for about the time it would take you to unload one -three holders, and then process those films together to see if any problems appear.

good luck, Bob

David G. Gagnon
4-Jan-2004, 20:55
Guy,

As in your previous qustion posted about this problem, I'm saying that this is a double image being produced by a void around the lens somewhere, even more so now that I've seen it. Have you tried a different lens/lensboard? Try that, and I'll bet that it will not happen.

DG

Richard Fenner
5-Jan-2004, 05:25
Further to John's comments, I once had a series of similar patterns on my slides, and with a polaroid back, eventually realised I could only insert the holder into one side of the back, not both sides - it went into both, but was very slightly loose on one, and that's the side that always produced the pattern.

Scott Walton
5-Jan-2004, 06:41
I was getting the same fogging about a year or so ago. It did turn out that I had some corners that were broken getting light in when the bellows was out and the sun hit it just right. In the photo, nice shot BTW, the sun is coming in from your right/rear so I would look for folds towards the rear of the bellows. In a darkened room, use a flash light on the outside of the bellows and looking inside (or visa versa if that is easier), move the flash light in every angle. At first, I thought mine came from not correctly seating my holders but it turned out to be the bellows. Camera Bellows (in the UK) is the place to get a new bellows. They are excellent craftsmen, very fast and a beautiful product! One other thing, check to make sure your back has good tension holding the back tight...

Ole Tjugen
5-Jan-2004, 10:22
I had a similar light leak - always parallel to the long side of the film. I eventually traced it to a strip of velvet which was missing from one side of the camera back. It originally had velvet light traps around three sides, but one had got lost somehow.

Guy Tal
5-Jan-2004, 18:29
Thanks everyone. I found and fixed the problem! I removed the bellowd and found that the leather separated slightly from the plastic frame near one corner. I haven't noticed it with my other lenses since the bellows wasn't fully stretched (as it was with the 300). A little super glue fixed it right up and I just got a couple of clean chromes back from the lab.

Thanks for your help!
Guy