Canon AE-1 light getting in.

[trainphotos]

How do i fix the decomposed seal on my camera? without having to go to a repairer.

[wolfeye]

You can buy these sheets of foam rubber called "Foamies" at Walmart (USA). They cost a buck or two. You simply use a tweezers to remove the existing light seal - it should come off in a single strip IF you can grab the backing. It's very tightly stuck-on in the Minolta SLRs I've replaced it in. Then cut the foamie to match with an X-acto knife.

Alternatively, you can search eBay for light seal kits. Someone makes them pre-cut, for most cameras.

BTW, the "Foamies" come in two flavors, one with a sticky backing, one without. I'd buy the the one with sticky backing, so you won't need to worry about what glue to use.