The strange case of the laser-like light leak on a Bessa-L

[Diapositivo]

I recently bought second-hand on an auction site a Bessa-L with a Voigtländer 15mm f/4.5. The lens is very, very, very wide angle and is not "easy" to use (to find a suitable subject), and I took a lot of time before taking 36 exposures. In fact, I rewound the film before the 36th exposure was taken, taking only 32 exposures.

On developing this first roll I had a surprise. The thirtieth image had a marked point-shaped leak which "burned" an area of complete underexposure. From that point, a thin stripe of blue-purple colour travels for 15 exposures toward the beginning of the film. The stripe is not continuous, it has some interruptions, it also changes direction at one point to become not any more parallel to the film edge. The first 14 and the last 2 exposures are not affected. It looks like a huge stripe of chromatic aberration. It is clearly visible in the slide cutter.

Before posting several images documenting the strange occurrence I would like to ask two questions to Bessa-L owners:

1) In your Bessa-L, is the foam running along the entire perimeter of the back cover, or it only exists above the film pressing plate and near the hinge?

2) Has this ever happened to you?

I suspect and I hope the culprit is the transparent slit on the back cover. That would show as a blue-purple light strike either because it comes from the back of the film and is filtered by some filter of the multi-layered structure or because it is the result of some light decomposition by the plastic window, as in a prism. Black electrician tape would be the remedy.

If the camera is supposed to have foam all around the back cover, then that's the problem. This camera is part light-trap, part foam. Not normal I say.

I hope the problem is not with the shutter itself leaking light. I also suppose that a light leak from the shutter would appear white.

Thanks
Fabrizio

 

[erikg]

It does sound like a pinhole type of light leak. I don't have a Bessa so I can't answer that part but I have seen similar defects. Taping up that window would be a good start. There could be some hole in the shutter but seems less likely as the Bessa doesn't have a cloth shutter, unless I'm mistaken. A close look at the shutter should tell you. I assume this was color film you were shooting.

 

[Diapositivo]

It was slide film. The Bessa-L has a metallic blade shutter. As every non-SLR, there is no mirror in front of the shutter so hypothetically leaving the camera in the sun, without lens cap, might damage the shutter. A cloth shutter would be damaged earlier, but I suppose there is a certain risk for any shutter, if temperature deforms some parts (maybe some plastic washers), dries lubricant etc.

The Bessa-L IIRC should actually have some kind of a double shutter, with a "safety" shutter in front of the actual shutter. But one can never know what kind of damage can be produced.

When I blow air with a blower brush I see the shutter blades moving. I don't know if this is normal.

Fabrizio

 

[artonpaper]

Check that there are no missing screws.

 

[Rol_Lei Nut]

Cut out a single piece of film (or use a whole roll if you're feeling wasteful - keeping the camera in the dark when advancing film) and put it in the film compartment (in the dark of course).

Take the lens off the camera and make sure it gets a healthy dose of light all around, then develop: that should pinpoint the exact location of the light leak.

 

[Diapositivo]

I've checked, no missing screws.

Rol_Lei Nut, if I understand you correctly, you suggest to keep the film still so that I will see a "point" rather than a stripe and that should give me more than a hint (well, at least, if it's not just behind the shutter, it certainly is a leakage from the back, and if it's near the slit, the problem should be there).

I'm not sure I would be able to do this with a stripe of film in the dark. I'll certainly feel wasteful and do as you suggest if the thing happens again.

In the meanwhile, has anybody any information about the light seals on the back of the Bessa-L?

I would suppose it's either the slit window, or some missing light seals. There is no "gunk" in the light traps, but I might have a badly-assembled camera.

I'll certainly put some electrician tape over the slit, from the outside, and see how it works (suggestions about better alternatives to electrician tapes would be welcome).

 

[Rol_Lei Nut]

Sorry if my suggestion wasn't especially clearly stated, but yes, you understood: if the film isn't advanced in the light, you could find the exact point of the leak (maybe, still might not distinguish between front & back).

For all kind of things, including closing the film advance "windows" on roll film cameras, I find that gaffer's tape does an excellent job. I also use it for all kinds of repairs (broken back latches) and for covering red dots and/or conspicuous names on cameras.