In article <4ahqog$1utk@ausnews.austin.ibm.com>, murali@austin.ibm.com says...
>I want to use different films ( e.g., ISO 100, ISO 400 ) at different >times. Can i reuse the film by rewinding and reloading at later time ?
>Does this affect in any way the pictures that are already taken ?

This can be done - it is easier with a camera that has either a manual rewind, or the ability to stop the motor rewind with the film tongue
left outside the cartridge trap. (Tongue extractors are available cheaply that allow you to put a roll of film back into the camera without having to move the film to a new cartridge.) If you load the camera carefully so that the film always loads the same way, you should not lose any frames (with luck) if you keep careful track of the number of frames exposed before removing the film. Be sure to advance the
reloaded film in the camera over the exposed frames with the camera set
on manual and the lens cap on (a high shutter speed and small aperture will help insure that the exposed part of the film will not be fogged).
Hope this helps.