What Are Light Seals and Why Your Camera Probably Needs New Ones

Light seals are a super important part of your film camera. Here is our guide all about light seals, what they are, why you need to replace them, and how to get them replaced.

Front light seal inside a Pentax ME

What are light seals?

So your 35mm film needs to be exposed to light, right? But only through the front of the camera, and when the shutter is open. This is where light seals come into play. 

Light seals block out any light that might spill onto your negative and into your camera. A few common places for this to occur are around the back door of your camera, where you load the negatives in; where the mirror hits the focusing screen in the front of the camera; in little gaps around your viewfinder and inner mechanisms. 

The light seals in the back of the camera stop light from spilling in through the gaps in the back door and onto your negative. 

The light seals in the front of the camera, where the mirror comes up, is sometimes referred to as the mirror dampener. It dampens the sound and impact of the mirror coming up when the shutter opens.

Some cameras also have light seals inside the camera, underneath the top and bottom plates. These have various functions depending on the model of camera.

Light seal in the front of a Pentax ME
Here you can see the light seal (mirror dampener) ​​in the front of a Pentax ME.

How do I know if my camera needs new ones?

It is important to make sure your light seals are up to date and have been replaced recently. 

The original material that light seals were made with perishes with age. It becomes a sticky, black goo. It's gross. 

It not only becomes much less effective at keeping the light out of your camera, but it can also cause other problems. 

Old light seals can cause problems in the mechanism of your camera, as they disintegrate and start to move around the camera as dust or goo. They can also get onto your negatives and damage them.

Light seals inside the camera
An example of internal light seals​​
Light seal degraded
What the goo can look like​​

When your camera doesn't have any film in it, get a small cocktail stick, and poke in the gaps in your back door. There are small slots where the light seals sit and the back door closes into them. If the cocktail stick comes away gooey, or you can't even see any seals in there, then they need replacing. 

You can check your front mirror dampener light seal by looking at it. They are normally quite obvious. 

Person replacing back door light seals

How do I replace my light seals?

It's possible to do your light seals yourself, but I highly recommend sending your camera to a professional to get this done. We offer this service for less than £30, and it assures that your light seals are perfect and correctly installed.

If you want to do it yourself, make sure you have the correct materials. You need a closed cell black foam in different thicknesses. The thickness of foam you need depends on the model of your camera. Avoid using standard black craft foam. 

The tricky part is getting the seals in the slots effectively and not covering any sensors or parts of the mechanism. 

We don't recommend taking your camera apart to do the internal mechanisms as you may do more damage to different parts of the camera and all the pieces in place.

Replacing your mirror dampener requires a particular kind of foam that you won't find at the craft store. It is possible to find it, but you need to be very careful when working around your mirror and viewfinder screen. Getting any goo on these parts will make the job a lot longer for you!

We accept light seal jobs, and you can send us an enquiry here.

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Max, owner of Cameras By Max

Article written by: Max

Max is the owner of Cameras By Max. They work full-time repairing and refurbishing all the 35mm film cameras you see on the website. Their favourite camera (at the moment) is the Olympus XA, and their favourite city in the world is Edinburgh.

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