Dennis Wingo: This is a two minute video that shows, about every 42 seconds, a shift in the video. This occurs when the line is scanned to the end of a framelet, over the calibration features that were pre recorded in the tape. Keith has posted images here that show the relationship between the scope trace and the dynamic range of the tapes. This gives us a qualitative measure of the performance of the tape drive. Even in its sub optimized state today, the scope trace almost exactly matches the original transfer function of the spacecraft film, thus giving us a means to evaluate the quality of the analog data derived from the tape.
Official website of the Lunar Orbiter Image Recovery Project (LOIRP)