Bronica S2/S2A back -- light leaks!

[Argenticien]

Hi all,

I've just obtained a second back for my S2. The new back is from an S2A (according to it's serial number ending in "S2A"). I found in my first rolls through it that it has a light leak like this:


Words to Live By by Argenticien, on Flickr

The leak is very obvious (like above) on some frames and very subtle on others (sometimes must temporarily do an outrageous levels adjustment in post to find it). But it's always more or less there. I think maybe the frames where it's worst are those immediately after a swap of backs (as I was switching between color and B&W that day), but my field notes (and memory -- it was six days ago ) are not detailed enough for me to be sure of this.

If it's in top-left of the pics, it should be at bottom-right of the film back, yes? (Photography 101.) I'm a bit at a loss to understand where to look for a leak on these backs: must it be where the dark slide lodges in its slot, or could it be a fault in the rubber ridges on the flat face of the film back? (Or elsewhere?). I see nothing obviously wrong on either. Any ideas?

I did find (there was a url link here which no longer exists) where Neil Poulson mentions two types of S2/S2A 120/220 backs. I was unaware of this until I found this leak and compared my two backs. This leaky S2A back is the type that has no sliding black curtain thing. My original back that came with my S2 is the kinds that does have the slider that rides the edge of the dark slide. I'm actually thinking light leaks should be less likely with the black curtain and I'm wondering why it was discontinued on the S2A backs.

Thanks for any insights.
--Dave

 

[Dan Daniel]

Nothing concrete to suggest. But I will throw out something I learned tracking down light leaks in another camera.

Be certain to look at the film position AWAY from the image area. So take your film as developed and position it inside the back with the leak on the frames both before and after the image opening.

I say this about your leak because it is rather distinct in shape, with one clean edge. Usually a dark slide leak with be cloudy and fuzzy. But if the leak is hitting the film as it either comes off of the roll or goes onto the take-up spool, the edge can be clean as the wound-up film stops the light. So look at how light could get into the spool area among other possibilities.

Oh, first question of any light leak: does it extend outside of the image area? Or does it stop at the edge of the image? This can elimate shutter/lens/film chamber leaks if it goes beyond the image area.

 

[Argenticien]

Be certain to look at the film position AWAY from the image area. So take your film as developed and position it inside the back with the leak on the frames both before and after the image opening.

Thank, Dan. Interesting, I hadn't thought of that. So really the leak could be almost anywhere! AUGGH!

Oh, first question of any light leak: does it extend outside of the image area? Or does it stop at the edge of the image? This can elimate shutter/lens/film chamber leaks if it goes beyond the image area.

Yes sorry I meant to put that in the original post. The leak does extend all the way to the physical edge of the film. It continues as a white stripe as shown in the pic I posted (black on the negative of course). It doesn't get wider, fuzzier, or more intense at the film's edge.

--Dave

 

[John Koehrer]

Because it varies in density it means the film is in position to fog for greater/lesser times.

Sacrificial film time? Load the sacrifice, advance to the second frame without making an exposure, then make an underexposed negative. Remove the back and expose it to a light source. Longer is better because you want the density on film.

Advance two frames, and do the same with the back On the camera. same drill with exposure, longer is better.

This gives you two exposed frames with a blank on each side. When it's developed you can load it in the back and get a decent idea of where the leak is.
The thinly exposed neg lets you position the film accurately in the film gate.

 

[Argenticien]

John, I was slowly resigning myself to the need for a sacrificial film. (Accepting that $4 test doesn't come easy for me; I'm a cheapskate!) But thanks for your advice on a process. It sounds very well laid out. I am usually a good isolator of variables and user of the scientific method, but I'm not sure I would have arrived at the sequence you describe. Great stuff! Hopefully this weekend I'll have time for the test. And I'll keep better notes than I did in the field last week. Also more data points should come in tomorrow when I get back the lab-processed color rolls from the same day as the above pic.

--Dave

 

[Dan Daniel]

Thank, Dan. Interesting, I hadn't thought of that. So really the leak could be almost anywhere! AUGGH![/I]

Oh you betcha- ARRGGHHH!! Light leaks can be very annoying. Especially because they often cannot be seen directly- you need to expose and develop film.

Here's a description of what I went through tracking down a leak in a Rolleiflex. No one- absolutely NO ONE- understands what was going on. My little film can baffle has been in place for two years now, including an overhaul by one of the best Rollei people, and NO MORE LEAKS! The repair people smile nicely at me and humor me by keeping the baffle in place...

http://www.rangefinderforum.com/forums/showthread.php?t=106282&highlight=2.8C+leak

Better luck with your leak! Check the hinge area and the latching area. See if the foam has dissolved away or such.

 

[Argenticien]

A new clue...

I got back my color films from the lab, and one of them shows something interesting (levels set in post to accentuate it):

We see that the same light-leak stripe appears above frame No. 1 of this film. So each frame that has the leak apparently got exposed on its way into the film gate, before it was the current frame. When I hold this neg in the film back insert, the stripe/leak is at the top roller indicated by the arrow in this picture:


Looking around inside this new-to-me S2A film back with or without the dark slide, with or without the film insert (using a penlight in a darkened room) I can see no light entering the film chamber near there, but it's hard to tell. Interestingly though, if I shine the light into the upper area of the film back where the film reminder frame is, or where the top body latches go, light goes right through, front to back, only a little bit on my good S2 back but a lot on my bad S2A back. This "shouldn't" matter because it's above/outside the actual film chamber. But I'm suspicious; it could be bouncing around off surfaces in there. Looking more closely, my good S2 back is felt-lined at the door closure (don't know if that's original or a prior owner's hack) while the S2A back is bare (S2 left, S2A right):

Similar for the door end that goes into there (S2 back felted, S2A not):


The felt appears to be why less light dances around the upper area on the S2 back. So I think I'm going to felt-line the door closure area on the S2A back (with some Jon Goodman felt that I have lying about) before I do a test roll of film. I suspect that at worst it won't help, but I don't think it can hurt. Hopefully if there's a leak there that I can't see without being able to put my head inside the closed film back then this might block it.

--Dave

 

[DWThomas]

For the two cents it may be worth, in its younger cousins, the SQ series (I have an SQ-A), light-struck patterns of the sort you're seeing are typically related to that closure area at the latch end. With those the material is foam which reverts to primal goo and tends to disappear. The felt type stuff is usually longer lived, but then your camera is no doubt considerably older. It does tax the patience.

Good luck with it.

 

[Argenticien]

Yes, what's weird about these backs: My older one has felt, and it's in good (not perfect, but good) condition. The newer S2A back has no felt, foam, or anything. It's not that there was some and it went to goo; there never was any. (Unless someone has removed it and meticulously, 100% perfectly, chemically cleaned off all traces of it.) I'm increasingly preferring the design and/or execution of the old S2 back. Anyway thanks Dave. It's encouraging that I may indeed be pursuing a solution in the right part of the back, based on your experience.

--Dave

 

[PRS-1]

Thanks for reporting on this. I don't know if it will help, but I have recently inherited the family Bronica S2 from my brother. The felt is mostly worn off on both back that I have. I just exposed my first roll of film. When I get it back, I'll see if I have any light leak issues that resemble yours.

 

[bobmolson]

[SQ film backs

For what it’s worth I had problems with some of my backs for the SQ. Even after installing news seals. So I took the easy way out. After loading the backs but before winding to frame one, I tape off all edges, sides, top, hinges and latches with black photo tape .. and no fog!!!! As I don’t reload in the field it is not a problem.

 

[Argenticien]

Update: I felted the S2A back so that it's lined in the same way the old S2 back is lined, as shown in post #7 above (pic #3). I did not felt the door end as shown in pic #4 of the same post, because on closer inspection, the S2A back doesn't need that; there's a light-trapping slot there. I then shot a test roll of Ilford Delta 100 Pro, somewhat in the manner John suggested (post #4 above). I sun-baked the camera and/or film-back in various ways--with the back on or off the camera, with or without the dark-slide in (the "without" only when the back was on the camera, obviously!). And exposed some frames but left the lens cap on for others to make the light leak stand out in a blank frame if it were there. At least eyeballing the roll while it is hanging to dry, I see none of the kind of light leaks shown in my original post. I'll scan the roll and amp up the brightness to see if there are any extremely dim leak artefacts not visible to the naked eye, but I doubt it. So apparently, the problem was up in the top of the film back and is solved by the added felt lining. Thanks to all for the advice and input. Forty-year-old piece of kit revived to work a few more years!
--Dave

 

[DWThomas]

Excellent! Good to hear of some progress in the desired direction.

 

[PRS-1]

[SQ film backs

For what it’s worth I had problems with some of my backs for the SQ. Even after installing news seals. So I took the easy way out. After loading the backs but before winding to frame one, I tape off all edges, sides, top, hinges and latches with black photo tape .. and no fog!!!! As I don’t reload in the field it is not a problem.

Good to hear this. I did two test rolls with my S2, one in each back. No evidence of light leak. The felt is wearing away, but thus far no trouble. What lens are you using? I have the original 75mm Nikkor. Initial results are good.

 

[zltnklzsvrjr]

Hi!

I was wondering if you are still active here? I have quite the same problem with my film back of my Bronica S2, having the exact same lights on the film after changing the backs on the body. But: I have two backs and none of them are felted, both the same inside and still, one does let light in, but the other. And I'm trying to figure out where might be the problem.

Let me know if you are still here
Zoltan