2017 January 12    Tech   Camera


The first article looked at overall camera maintenance, starting with inspection. 

Now let's talk about light seals, the most common thing to go wrong with old film cameras.

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In This Article

Bad Light Seals

Tools Needed

Replace The Seals


Bad Light Seals

If you shoot film, you're supposed to check the light seals in your camera periodically. 

The reality is that many of us wait until we get back a roll of film that has mysterious bright zones.  This is what they might look like:

You don't have to wait until this happens.  Checking for bad light seals is very easy.  All you have to do is open up the back of the camera (with no film in it) and look closely at the foam seals.  If they're deteriorated like the ones shown at the top of this page, they will need replacement.

One thing I would caution, though:  old light seals can look OK from year to year, and then suddenly they crumble.  This happened to my Minolta X-700.  Up until I had those mysterious bright zones in a roll of pictures, I thought the light seals looked OK.  But once the light leak happened, the seals were a disaster when I checked them.

Large format shooters, you might also want to be inspecting those film holders.  They, too, can occasionally have light leaks.  I did not know or think of this until I had one that fogged film, ever so slightly.

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Tools Needed

The most specialized tool you'll need is one you can probably make yourself.  Basically you want a thin piece of oak, ash, or something like that, with the end fashioned into a chisel point. It's like a giant toothpick, but instead of the end being pointy, it's flattened.  That allows you to remove deteriorated light-seal material.

If you don't have oak, etc., bamboo works too.  Chopsticks work great;  that wasn't my idea, but now I can't remember who first suggested it. 

Other tools and materials you will need:

Utility knife.  It also helps if you have a metal straight edge.

Foam brushes.  You cut these into thin strips and use that as your light-seal material.  Get an assortment;  make sure it includes some of the larger ones.  You'll want to be able to cut continuous long pieces, instead of a bunch of short ones.

Glue.  There are only a few types that work well for this.  The glue should be thick, it shouldn't dissolve the seal material, and it should remain flexible when dry.  Many people use this stuff, but if you ever have to replace the seals again (which you will), you might find it difficult to remove. 

I use an extra-thick PVA craft glue, which doesn't adhere to metal that well.  But it adheres well enough to hold the light seals in place, and that's all you need.  Another good choice would be this.

Tweezers.  For positioning the light seals before the glue sets.

Toothpicks.  For removing excess glue, because otherwise it would look very sloppy and the camera back might not close properly.

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Replace the Seals

First remove the old seals.  Because my Minolta has some plastic, I would not use acetone or lacquer thinner.  It's a better idea to start with denatured alcohol.  Naphtha or mineral spirits should also be OK.  I can't think offhand of any plastics they would dissolve, but it's possible. 

Once the old seals are gone, let the solvents evaporate.  Then, apply a thin layer of glue where the seals will go.  I would apply only enough glue for one seal at a time, because otherwise the glue will dry by the time you get to it. 

The typical 35mm camera is fairly simple.  Pay special mind to the light seal that goes along the hinge.  This is the hinge that holds the back onto the camera.  The pictures that you've already shot are on a little spool right near that hinge.  Bad light seals here can wreck a lot of photos.

Some cameras have light seals running the whole length of the back, parallel to the film track.  Other cameras, such as the Minolta X-700, have them going only partway.  If they don't run the whole length of the back, there might be a reason.  I would recommend just copying the old light seals. 

Not the best-looking seals?  No problem.  All they have to do is work.

Most 35mm SLR's have a little lever or button that controls the frame counter.  Make sure you don't cover this with seal material, or it won't work properly.  It helps to photograph everything before you remove the old seals.

As I said, 35mm seals are generally simple.  Where the process gets tricky is when you get into cameras that have revolving backs and that sort of thing.  I still haven't installed the light seal kit on my Mamiya RB67.  It's been sitting around all this time. 

Also, I don't know that black yarn or black felt would work on a camera like the RB67.  I do know that it works on a lot of 35mm cameras;  I have used these to re-seal several cameras, with good results.  The one caution is that yarn doesn't compress quite as much as foam.  The camera back could become a bit more difficult to close.

The only other note I can think of here:  let the glue dry with the camera back open.  Let it dry a couple days before you test it.  If you close the camera back while the glue is still wet, it will eventually dry, but it will be very slow. 

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This was a quick look at replacing light seals on a film camera.  Although every camera model is a little different, there are some basic elements that remain the same.  Once you figure out how to do one camera, you should be able to apply that knowledge to others. 

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