Film Camera Light Seals: How to Replace Them Yourself

The following video (in English, with German subtitles) shows the process in detail:

 

If you own one or more analogue cameras, there’s a good chance that the light seals need to be replaced in one or all of them.

Over time, these small foam strips deteriorate and can cause light leaks that may completely ruin your photos in the worst case. In any event, image quality suffers, and the vast majority of cameras available on the used market—especially from private sellers—are sold with defective light seals.

 
Unless the seller explicitly states otherwise, you can assume that a camera is being sold with defective light seals.

Photo: So-called light leaks caused by defective light seals

Replacing the seals takes some time, patience, and perseverance, but even beginners can do it easily on a quiet afternoon. In this guide, I’ll show you step by step how to replace the light seals, exactly as we used to do in our small camera workshop. We sealed hundreds, if not thousands, of cameras this way, and it always worked reliably.

What you need

• Pre-cut light seal kit or foam sheets in various thicknesses to cut to size
  • You usually need a 1 mm-thick sheet for the seals on the back panel (cut the strips to approximately 1.5 mm wide)
  • and a 2 mm-thick sheet for the mirror bumper
• Utility knife, ruler, and cutting mat (for those cutting their own strips)
• Scissors for cutting the strips to length
• Cotton swabs
• Isopropyl alcohol (for removing the old seals)
• Scraper for removing the old seals (no sharp metal tools, as they will scratch the camera finish)
• Tweezers for precisely positioning the new seals
• Residue-free removable shutter curtain protector (to cover the shutter curtain during cleaning)
• Microfiber cloth and toothbrush (for final cleaning)

In our ready-to-use light seal kit, the pre-cut strips, mirror bumper, cotton swabs, tweezers with a scraper on the back end, shutter curtain protector, and instructions are already included. For the replacement, you only need isopropyl alcohol and scissors.

Photo: Contents of the Ausgeknipst light seal kit with pre-cut light seal strips, mirror stop damper, cotton swabs, tweezers with scraper, and instructions. The photo still shows the old masking tape used as a shutter protector. The kit now includes a shutter curtain protector instead, which can be removed cleanly.

Which cameras is this guide suitable for?

The process is almost identical for most 35mm SLRs, such as the Canon AE-1, Olympus OM-1, Pentax ME, or Minolta SRT series.

Step 1: Remove the old light seals

Before you begin:

• Stick the shutter curtain protector from the kit over the sensitive camera shutter (the curtains in the middle of the camera body) so that no old seal residue falls into the mechanism. Leave it protruding slightly on the left; you can later pull it off cleanly using this tab. The shutter curtain is paper-thin and extremely delicate; never touch it with your fingers or tools.
• On almost all the cameras mentioned here (Canon AE-1, Olympus OM-1, Pentax ME), the back can be detached without tools: Pull the small spring-loaded pin on the hinge downward, and the door will come loose. Working on a detached back is much easier and also provides additional protection for the shutter.

You will usually find the old seals:

• Along the top and bottom edges of the back door

• Around the hinge of the back door

• At the mirror stop damper (not actual sealing material, but it should often be replaced)

How to remove the old seals:

1. Apply isopropanol to the old seals with a cotton swab.

Photo: Old seals can be dissolved with a little isopropanol and are then easier to remove.

2. Wait briefly until the material softens, then carefully scrape it out with the scraper on the back of the tweezers. Avoid using sharp metal tools directly in the grooves; they can scratch the camera's paint, which may later cause unwanted reflections.

Photo: You can carefully scrape away the old seals with the back of our tweezers. Do not apply too much pressure, or you could damage your camera's paint.

3. Make sure no residue falls inside the camera.

Photo: If old sealing material falls inside the camera, hold the camera with the opening facing downward and carefully brush it out with a soft brush. A blower bulb can drive sticky particles deeper into the mechanism or mirror box. Sometimes it also helps to tap the back of the camera lightly. Carefully: like a baby who has choked ;)

4. Finally, remove the last particles with a cotton swab soaked in isopropanol 

Photo: To remove the last remnants of the old light seals, you can tear off a piece of cotton from a cotton swab with your fingers, clamp it in tweezers, and dip it in isopropanol. Then run the soaked cotton ball along the seal groove until the cotton remains completely white. The more thoroughly you do this, the better the new seals will adhere later.

 

Photo: Removing the crumbling mirror stop damper from a Pentax ME Super

Tip: Be especially careful when removing the upper and lower door seals. No alcohol should get into the film counter mechanism (usually at the top right of the back), as it could damage the mechanics.

Photo: At this point, most cameras have a small opening for automatically resetting the film counter. No old sealing material should get in here, as it could block the mechanism. 

Step 2: Insert the new light seals

After cleaning, you can insert the new seals:

1. Cut the new strips to the length of the groove with scissors. If you use foam sheets, cut them to the required width as well.
2. With pre-cut adhesive seals, peel off the protective film in stages (only 2–3 cm at a time), not all at once. This prevents the exposed adhesive from sticking to the tweezers or the wrong places.
3. Press the strips into the correct position with tweezers.
4. At the hinge, make sure the seal is seated properly and that the door still closes easily.

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

The trickiest part is the thin seals along the back-door grooves. If they twist, just stay calm and press them into the groove with the tweezers. These self-adhesive strips are a little more fiddly to position, but you won’t need to buy any special adhesive.

The isopropanol trick: Lightly moisten the adhesive side of the self-adhesive seal with isopropanol. This temporarily reduces the adhesive’s grip for about 1–2 minutes, allowing you to slide and adjust the strip in the narrow grooves with ease. Once the alcohol has evaporated, the adhesive holds extremely firmly.

Adhesive-free alternative: If the adhesive method causes problems in the particularly narrow grooves, you can leave the protective film on completely and simply press the strip into the groove without adhesive. The friction in the narrow groove keeps the foam securely in place even without adhesive.

Step 3: Replace the mirror bumper

1. Find the old mirror bumper (usually a strip of foam above the mirror).
2. Remove it carefully so that no particles fall into the mirror box.
3. Cut the new bumper to the appropriate size.
4. Use the tweezers to place it precisely in the correct position.
   
   

Photo: Installing the new mirror bumper

Before removing the old bumper, cut a small piece of Post-it and place it over the mirror and focusing screen before you start scraping. This prevents sticky crumbs from falling onto the delicate surfaces.

Do not get alcohol on the focusing screen! It may be permanently damaged.

Step 4: Final cleaning and inspection

• Carefully pull the shutter curtain protection strip off the shutter curtain by its tab.
• If you removed the back, reinstall it now.
• Close the back door and check that all the seals are seated properly.
  
  

Photo: Finally, clean the outer housing with a slightly damp microfiber cloth and a drop of dish soap. Avoid wet brushes: water must not get into gaps in the housing or the electronics.

 

Conclusion

Done! Your camera now has new light seals and should work perfectly again—goodbye, light leaks!

This guide is designed for 35mm SLRs, but with minor adjustments it can also be used for medium-format cameras or film cassettes.

If you have any questions, feel free to leave me a comment or send us a message via the contact form in our online shop :) I’m looking forward to photos of freshly resealed cameras!

 

Have fun taking photos and best regards, your Vladi!