I have noticed light leaks on my FED I (Barnack copy). Sometimes it is more obvious (like in attached photos), sometimes less, sometimes not at all.
Question: how can I fix this without sending the camera away and keep the cost at minimum? Some paint - which one, where to buy it in EU? Or black marker? It does not have to be permanent solution, I will use this camera seldom - just for a review and test.
Exactly. Someone let the sun shine though the lens onto the shutter and burned a hole, possibly. A new shutter will cost more than another camera. Perhaps you can patch the hole with some light-tight but thin material.
I recommend Golden Heavy Body Artist Paint #1040 Carbon Black http://www.goldenpaints.com/products/colors/heavy-body/carbon-black or its equivalent in you part of the world. 2 or 3 thin coats are better than 1 heavy coat. Use a fine bristle artist brush to apply. Thin the paint to make thin application easier.
This paint remains flexible when dry and does not flake off.
Solvent diluted liquid electrical tape (don't know what the local brand is) is also reputed to work well. IIRC you 'd use liquid tape and xylene in equal proportions. I will be trying this soon on my Zarya. Now to find some xylene in less than gallon quantities.
Never seen anything like this in Germany.
But I once bought an elastic black varnish to put onto leather.
Anything elastic might stick onto another layer of the curtain. But one might keep a camera with a curtain repaired this way in the position with the repaired location exposed.
Though that rises the risk of fogging once the repair fails...
All the kids here use a fabric paint on tea shirts.
It survives the front loader...
You apply and leave the camera 48 hours on shelf to stop being sticky.
Works ok on Nikon F2 metal shutters or leather bellows.
Thin so you can use several coats.