How to Replace the Light Seals on Your Film Camera

The video below (in English, with German subtitles) shows the whole job in detail:

 

If you own one or more film cameras, chances are that some or all of them need new light seals.

These little foam strips break down over time and can cause light leaks that, at worst, ruin your photos completely. Either way, your image quality suffers. The vast majority of used cameras, especially those from private sellers, are sold with deteriorated light seals.

Unless the seller specifically states that the light seals are in good condition or have been replaced, you can assume they’re bad.

Photo: Light leaks caused by deteriorated light seals

Replacing them takes some patience, but even a complete beginner can manage it on a quiet afternoon. The steps below are exactly the ones we used to follow in our small camera repair workshop. We’ve resealed hundreds, if not thousands, of cameras this way, and it has always worked reliably.

What you’ll need

• A pre-cut light seal kit, or foam sheets in various thicknesses to cut yourself
  • If you’re cutting your own, you’ll usually need 1 mm sheet for the seals around the camera back (cut the strips to about 1.5 mm wide)
  • For the mirror bumper (the foam strip the mirror flips up against when you fire the shutter), you’ll usually need 2 mm sheet
• Craft knife, ruler and cutting mat (if you’re cutting your own)
• Scissors to cut the strips to length
• Cotton swabs
• Isopropyl alcohol (to remove the old seals)
• A scraper to remove the old seals (not a sharp metal tool, which will scratch the camera’s paint)
• Tweezers for placing the new seals precisely
• Tape that peels off without leaving residue, as a shutter curtain guard (to cover the shutter while you clean)
• A microfiber cloth and a toothbrush (for the final clean), plus a soft brush (to brush out any loose bits)

Our ready-made light seal kit already includes the pre-cut strips, the mirror bumper, cotton swabs, tweezers with a scraper on the back end, the shutter curtain protector and instructions. All you need to add for the job is isopropyl alcohol and a pair of scissors.

Disclaimer: We sell some of the products mentioned here. Even so, this article is meant first and foremost as a helpful guide, not as a sales pitch.

Photo: What’s inside our Ausgeknipst light seal kit: pre-cut light seal strips, mirror bumper, cotton swabs, tweezers with scraper and instructions. The photo still shows the masking tape we used to include as a shutter protector. These days the kit comes with a shutter curtain protector instead, which peels off again without leaving any residue.

Which cameras does this guide work for?

The process is almost identical on most 35mm SLRs, for example the Canon AE-1, the Olympus OM-1, the Pentax ME or the Minolta SR-T series.

For two Canon models, iFixit has dedicated illustrated guides showing where the strips go on each body: one for the AE-1 Program and one for the A-1. There’s one point where we do things differently from the A-1 guide: we brush loose crumbs out rather than blowing them away with a blower, because the blast of air can drive sticky residue deeper into the mechanism.

Step 1: Remove the old light seals

Before you start:

• Stick the shutter curtain protector from the kit over the delicate shutter (the curtains or blades in the middle of the camera body) so that no bits of old seal fall into the mechanism. Leave a little overhanging on the left: that overhang is the tab you’ll use later to peel it off again without leaving any residue. The shutter (cloth curtains or thin metal blades, depending on the camera) is extremely fragile: never touch it with your fingers or with tools.
• On the Canon AE-1, the Olympus OM-1 and the Pentax ME, the back comes off without any tools: pull down the small spring-loaded pin on the hinge and it releases. With the back removed, it’s much easier to get at the seals, and the shutter gets extra protection as well.

You’ll usually find the old seals:

• In the grooves along the top and bottom edges of the body opening

• Around the hinge of the camera back

• In the mirror box: the mirror bumper (not a light seal, but it often should be replaced at the same time)

How to remove the old seals:

1. Apply isopropyl alcohol to the old seals with a cotton swab.

Photo: A little isopropyl alcohol softens the old seals, making them easier to remove.

2. Wait a moment for the material to soften, then carefully scrape it out with the scraper on the back end of the tweezers. Don’t use sharp metal tools in the grooves: they can scratch off the paint, and the bare spots will reflect light later on.

Photo: You can use the back end of our tweezers to gently scrape away the old seals. Don’t press too hard, or you could damage your camera’s paint.

3. Make sure no debris falls inside the camera.

Photo: If any old seal material falls inside the camera, hold the camera with the opening facing down and gently brush it out with a soft brush. A blower can push sticky particles deeper into the mechanism or the mirror box. Sometimes a light tap on the back of the body helps too. Gently: like patting the back of a baby who’s swallowed something the wrong way ;)

4. Finally, wipe out the last traces with a cotton swab soaked in isopropyl alcohol.

Photo: For the last bits, pull a small tuft of cotton off a swab, grip it with the tweezers and dip it in isopropyl alcohol. Then keep running the soaked cotton along the channel until a fresh piece of cotton stays white. The more thorough you are here, the better the new seals will stick later on.

 

Photo: Removing the crumbling mirror bumper from a Pentax ME Super

Tip: Take extra care when removing the top and bottom seals. Make sure no alcohol gets into the frame counter mechanism (usually at the top right), as it can damage it.

Photo: Most cameras have a small opening here for the automatic frame counter reset. Don’t let any old seal material get in, or it can jam the mechanism.

Step 2: Install the new light seals

Once everything is clean, you can install the new seals:

1. Cut the new strips to the length of the channel with scissors. If you’re using foam sheets, you’ll also cut the strips to width yourself.
2. With self-adhesive strips, peel the backing off in stages (only 2-3 cm at a time) rather than all at once. That way the exposed adhesive won’t stick to the tweezers or to the wrong spots.
3. Use tweezers to press the strips into position.
4. Around the hinge, make sure the seal sits properly and the back still closes easily.

Photo: New light seals are best positioned precisely with tweezers.

The trickiest part is getting the thin strips into the narrow channels. If they twist, just stay calm and press them into the channel with the tweezers. Self-adhesive strips are a bit fiddlier to fit, but you don’t need to buy any special glue.

The soapy water trick: If the strips still stick too soon, peel off the backing completely and briefly dip the strip in water with a drop of liquid soap. The adhesive then won’t grab for a minute or two, so you can take your time sliding the strip into the narrow channel and pressing it all the way to the bottom before it sticks to the side walls. Once the water has dried, the adhesive holds as usual. We owe this tip to a customer with a Canon F-1, whose channels are especially narrow and deep: at first several strips tore while they were fitting them, but with soapy water it went without a hitch. We then tested the trick with both soapy water and isopropyl alcohol, and soapy water works better.

No-glue alternative: If sticking the strips down in the especially narrow channels doesn’t work, you can also leave the backing on and press the strip into the channel without adhesive. Friction in the tight channel holds the foam reliably in place, even without glue.

Step 3: Replace the mirror bumper

1. Take the lens off and, looking into the mirror box from the front, find the old mirror bumper (usually a foam strip above the mirror).
2. Remove it carefully so no particles fall into the mirror box.
3. Cut the new bumper to size.
4. Use the tweezers to place it exactly in the right spot.
   
   

Photo: Fitting the new mirror bumper

Before you scrape off the old bumper, cut a small piece of Post-It to size and use it to cover the mirror and the focusing screen (the screen sitting above the mirror, where the viewfinder image is formed). That way no sticky crumbs can fall onto these delicate surfaces.

Keep alcohol away from the focusing screen! It can damage it permanently.

Step 4: Final clean and check

• Carefully peel the shutter protector off again using the tab.
• If you removed the camera back, put it back on now.
• Check that all the seals are sitting neatly, then close the back.
  
  

Photo: To finish, clean the outside of the body with a slightly damp microfiber cloth and a drop of dish soap. Don’t use a wet brush: water must not get into the gaps in the body or into the electronics.

 

Done! Your camera now has fresh light seals and should be light-tight again. Goodbye, light leaks!

This guide is written for 35mm SLRs, but with a few small adjustments you can also use it for medium format cameras or film backs.

If you have any questions, feel free to leave a comment or get in touch through our contact form. I’d love to see photos of your freshly sealed cameras!

 

Happy shooting and all the best, Vladi!