How to tell if a roll of film is used already?

so i bought a lomo fisheye camera a few months back and took some pictures with it until the roll was done, however when i put the roll of film back in the canister i didnt mark it so now i have four canisters with film rolls in them but not sure which is the one i used already, the others were not used so i was wondering if there was a way i could tell a used roll of film from a unused one,thanks in advance



normally when film is rewound it goes entirely back inside the cassette. you should have 3 with a pigtale of film ready to load, and one that does not have a film end showing.




Did you try holding it up to a light to see if you can see the pictures in it. Or my other suggestion: just buy a digital camera :D.