I know this is dumb, and I probably know the answer, but here it goes:

I keep my fresh film in the plastic cases they come with (pill box looking plastic cases) on one side of my desk, and on the other I keep my used film in the same sort of cases. While my house keeper was cleaning up she mixed up the both sides into one neat little pile, how do I tell them apprt?

theres no way of telling by looking at the rolls. Both have a little bit of film sticking out so visually they are all identical.

These photos are valuable to me and I need them to make my self money

Is this a live and learn experience or is there something i could do, other than develop 40 rolls of film

Thanks,
Michael

Perhaps I'll rephrase your question to, "is there something i could do, that's cheaper than developing those 40 rolls of film?"

There is probably no way to visually see which ones are exposed or not, unless the length of the tab is amazingly consistent, and different between used/unused.

When you load the film in the camera though, you pull the film out about three inches. This bit of film immediately becomes completely exposed. You could pull about two inches off each roll and develop them. That will show which ones are unused, and which have been used.

Before doing this, check that whoever develops your film can do so, with film that's cut to a square end since the tab is now gone. And you may need to cut a rough tab onto the unused rolls to load them (they're now 22 frame rolls...)

It's only really worthwhile doing all this if those unused rolls are really precious!
Andy

If you used an older style 35mm where you inserted the film in a slot on the take up spool, it will leave a faint fold in the tongue on used film.

Michael,

If you really can't see any physical difference, then this is a learning experience. You'll just need to process all the rolls.

You'll probably figure out a way to mark your shot film in the future. I always left the leader out (as you did), but tore off the end to mark the shot film. You can fold it over, mark with a Sharpie marker, wind it all the way in, put the film in the can upside-down, put tape over the end of the film, put shot film in an envelope or plastic bag, etc.

The key is to do this consistently, of course.

--Ken

That would have been my recommendation as well. I used to wind the film back to about a cm and fold it over so I knew which rolls were exposed.

Mike.

True! thanks a lot, this helps

Now I just gotta go through 40 rolls with a magnifying glass

And thanks everybody for the tips. I'm sure this will now never happen again.

Michael

An even better approach to preventing a repeat is to wind the film all the way into the exposed canisters, so that there is no tail protruding from the canister of used rolls. That makes it impossible to re-use a roll accidentally.