Say if I wanted to try out double exposure. Could I just go at it, shoot a roll, rewind it almost to the end and shoot again at random ? Or would I just be wasting precious film ? Because it seems difficult to remember each picture you took in the right order so you can re-expose it with something you think'll fit.
theres a couple of things to keep in mind if your gonna try that.
1. you might wanna try shooting it at least a half of a stop down both times, because exposing each frame to double the amount of light would probably blow out most of the image (of course, all depending on what your shooting and exposure levels and stuff, but just keep in mind that you'll run the risk of bombarding your film with double the amount of light you normally would)
2. Getting the frames to line up is a total crap shoot. unless you make some kind of mark on the small strip of the first legnth of film that you expose when loading you camera, so that you can line up the exact same sprocket holes with the advancing spool, and even then they might be slightly off due to the tension in the film being stretched over the back.
3. after shooting the first time though, you'll have to keep a very keen ear to your camera to make sure you rewind the film enough to have the still light sensitive areas in the canister, but also leaving a little tail to reload with, cause using one of these things:
is a pain in the ass.
that being said, try it anyways. who gives a fuck if the frames don't line up perfectly, or if the density of your images get a little muddy/blown out/under done. double exposures are a roll of the dice most of the time anyways.