A film scanner scans original film stock from 8mm to 70mm. Some models of film scanners scan each frame individually, locked down in a pin-registered film gate, taking a few seconds of scanning time per frame, as opposed to continuous film scanners, where the film frames are scanned as the film is continuously moved past the imaging pic up device. However, the last is being mainly used on low-resolution acquisition. So how does it work? Without diving deep into the technicals, we can say that the film scanner scans the film frames into a file sequence, whose single file contains a digital scan of each still frame.
This file is pretty heavy and stores color information as raw data, preserving the optical characteristics of the film stock. Then the files can be played on any NLE. Then the scanned footage can be edited and mastered back on film when needed (theater projection for instance). However, most of the projectors are digital, hence this process is mainly one-sided. Now, imagine scanning the mighty 65mm film from n IMAX cameras.
Source: IMAX Shows How its 65mm Film is Scanned – Y.M.Cinema – News & Insights on Digital Cinema