Early proving tests of the film gate and film advance mechanism were done using both winding arms taken from a film editor so feed and take-up reels were manually operated. Photograph 25 shows the Mark 1 model that captured from the base layer side of the film. The film runs from the feed reel, upwards through the film gate, via the tension sensor, to the driven take-up reel. Rewinding the film is done manually directly from reel to reel. Later the introduction of a driven take-up reel with a tension sensor importantly avoided vibration caused by the action of manual winding and kept a low consistent tension on the film as it exits the film gate. The weight of the winding handle on the feed reel causes variation in the pull required to advance each frame but no loss of consistency in frame-to-frame positional accuracy was observed. This consistency of position is essential for high quality captures.
The major differences between the Marks were:
1. Mark 1 and 2 captured from the base layer whereas Mark 3 did it from the emulsion side.
2. Mark 1 and 2 used a 10-Watt halogen lamp whereas Mark 3 used a LED.
3. The Mark 3 used a mirror image of the original film gate, the cam rider was flipped to allow its claw to engage the film correctly in the film gate and the bias spring anchor was re-sited.
4. Rewinding the film on the Mark 3 model is done manually using a detachable handle fitted on the static feed reel axle and directly from reel to reel.
5. To avoid generation of vibrations when a frame is being captured the Mark 3 only winds the film during the latter part of the cam’s rotation i.e., as the film is advanced
Photograph 26 shows the Mark 2 model that was made for a friend Stan Pow who had taught my son and me how to edit video using Adobe Premier 5.1 with QuickTime. He liked the quality of the telecine transfers I had made and, as he is a retired BBC video editor I greatly value his opinion and help. The Mark 2 mechanics were the same as the Mark 1 and it captured from the base layer side of the film. To generate the pulse streams I developed a unit using 555 timer integrated circuits. The PC starts the pulse generator and a vane sensor mounted on the sledge is used to detect when the cam has rotated 360° and reached the home position again to stop the pulse generator. Photograph 27.