What happens if i rotate the film rewind?

Question

Can someone tell me what happens if I rotate the film rewind(back cover open knob) when the film is still in the camera? I accidentally moved it.

Answer 1

The film "rewind" crank is usually directly connected to the shaft of the supply spool. Trying to wind it in the back direction with the film still in the camera and not released (usually a button needs to be pressed somewhere) will just tighten the film against the sprocket that is trying to hold the current frame in place. If you keep cranking, the first thing to give is probably the film ripping at the sprockets.

If you crank the other way, you loosen the film on the supply reel. If you go too far with that, and there is space available, the film will actually be wound around the supply reel again but in the opposite direction. This by itself causes no harm, but during the cranking the film can get damaged due to being bent in a fairly tight radius, nearly folded. It will also rub against itself, possibly causing scratches or other abrasions.

So no touchy da cranky thing until you actually want to rewind the whole roll.

Answer 2

As noted in another answer, if you turned it in the "rewind" direction most likely you just tightened the film. You'd probably know it if you snapped the film. If you turned it the "wrong" direction you introduced some slack and might end up with a little bit of a ripple in the film being exposed if the film backing support isn't in perfect condition.

Now, if you were not stopped from rewinding the film by the "release" button - either you pressed this button or the release mechanism has been worn down - you might end up with a double exposure on that film. Note that exposures are additive, not averaging, so if you have a double-exposure situation the result will be very light in the final output. If you don't want that, you can advance the film the other way by snapping a "black" photo (lens cap on) and advancing. Might waste some of the film doing this, but perhaps that is better than the chance of wasting the previously-taken photo.