Replace the Light Seals of Your Good Old Film Camera




I love fixing things...

Most film cameras have light seals at the door rims and mirror rest (SLRs only). These are made of some rubbery foams and they degrade over time. Considering that most of these tank-like cameras are over 20 years old, it is very likely that your camera is suffering from light seal degradation. Rotten seals will not perform as they should and leak light through the film door or the viewfinder.

Moreover, when degraded, the rubbery foam turns into a goo-like substance which will stain your focusing screen, mirror, or lens, contaminate the film compartment and even crumble over your film. It is very sticky and nasty, so it gets harder to clean when it gets worse.

But, you can find replacement light seals in bulk from ebay (search: light seal replacement, i.e., this one). Unless they are custom made, they are sold in bulk packs which you can cut/customize for your needs (most sets can fix over 3-4 cameras).

This instructable will show you how to apply them. I will start with my old Canon F-1 (I sold it long ago unfortunately). It was in great shape, except for the rotten foam light seals. They needed to be changed in time, so here is what we'll do next:

1. Identify and document the existing rotten seals,
2. Scrape off the seals, clean the surface,
3. Cut the new seal foam in correct size and shapes,
4. Apply the new seal foams in places.

There is not much risk in this operation, but you can still ruin the focusing screen, the mirror, and the shutter curtains if you are not careful. So be warned, and don't start if you don't feel comfortable.

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Step 1: Inspect the Existing Light Seals for Condition.

Look at the photos in this step, I have notes on them, and they are pretty self explanatory.

Step 2: Clean the Film Door Area.

Here we'll strip the goo-like rotten foam off the film door area. We'll use an alcohol based solvent to soften it, and strip it off using a bamboo skewer. In my case, the cleaning skewer came with the new foam set. Look at the photos below, I have notes on them.

Be careful to keep your fingers off the shutter curtains. They are very fragile, you don't want to ruin them.

Step 3: Clean the Mirror Box Area.

With a Canon F-1, this step is much easier to accomplish, because it has a detachable viewfinder prism. There is virtually no risk of contaminating the focusing screen (which is so fragile). If you are working on a camera with fixed prism, be very careful and do not ruin the focusing screen (it cannot be wiped, cleaned, and it is easily marred).

Be careful and do not touch on the mirror. It can be stained/damaged very easily.

Step 4: Measure, Cut and Stick Foam Seals for the Mirror Box.

Use a small ruler to measure the necessary dimensions for the mirror padding foam. Check out the photos below for notes.

Step 5: Replace the Foams for the Film Door Edges, and the Hinge Area.

Here we'll use the strip foam to replace the old foam for proper light sealing at film door area. Look at the photos below for notes.

Step 6: Finished!..

You have a light-tight camera now, go back to snapping awesome photographs on a wonderful medium: film!..

Any questions or comments, you are welcome to contribute.




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    18 Discussions

    Two Wheels Good

    Question 3 months ago

    Very informative. Thanks! A few questions if you don't mind... Does the mirror pad have to be light tight? I thought it was just to cushion the impact and that any light getting above it would not make its way onto the film but that is just my guess. Also, would the more dense foam sheets you get at a craft store be okay for the mirror pad? Finally, before seeing this guide, some of the disintegrating mirror pad foam got on the focusing screen and I wiped it and got the dreaded black streaks. Can I gently work it away with the alcohol solution or will I have to put up with seeing this through the viewfinder?


    1 year ago

    i have found the best way to cut self adhesive light seal is with a paper trimmer paper side up this will cut perfect any sizes required much easier than a model knife. readily available at any stationery shop or on line.


    9 years ago on Introduction

    Hi. Could you help in order to repair/replace the back door (film door) foam seals in a Canon A-1? Thanks a lot.

    2 replies

    Reply 9 years ago on Introduction

    There's a guy on ebay who sells the foam, and he includes some instructions with it.

    eBay user interslice sells kits for the A-1 and most of the A-series.
    Around $9-$10 shipped, it's a great deal of savings versus camera shops charges of $100-$300 to "clean" it.


    10 years ago on Step 4

    Sorry if I missed it but I am wondering where you got the mirror padding?

    1 reply

    Reply 10 years ago on Introduction

    The mirror padding came with the replacement light seal set I bought earlier. I just cut it into the right size and shape (which, I think, is missing in the instructable). K.


    Not really, if you are careful with the sticky goo shavings, it should be alright. Once I was doing this on an SLR with fixed focusing screen and a tiny piece stuck on the matte surface of the screen. Then I tried cleaning it and ruined it all over. Don't do that!.. :-)



    11 years ago on Introduction


    2 replies

    11 years ago on Introduction

    very nice. i just ordered some of this foam for an olympus pen half frame camera. i first went to a shop where i was told that i would have to send it to olympus and it'd cost 150 € to repair :D

    1 reply

    Reply 11 years ago on Introduction

    Good job!.. half-frame rocks! I used to have a russian made half frame camera at uni years, before the digital revolution. It was fun. I was taking tons of pics of my friends and then scanning them and emailing... Serious fun. :-) Good luck... K.


    11 years ago on Introduction

    now this seems good :) as long as i'm careful :) I'll have to check my foam seals now (well wen the film is spent at least) (Minolta XE-1)

    1 reply