It is possible to make a high quality system for transferring film motion images into video images at reasonable cost.
The use of a reversed camera lens to provide the video camera with the required macro facility worked well. The three lenses tested were all colour corrected, of 50 mm focal length, from reputable manufacturers: Pentax, Minolta and Nikon. The lens is set to its maximum aperture using its manual setting for this use. A Canon FD lens could not be tested as manual aperture setting was only possible when mounted on its original camera body. The captured video images were sharp and colour rendition was not noticeably degraded by the additional lens. The video camera’s zoom facility made possible the accurate coverage of both film format image sizes.
The film frame to frame registration was excellent limited only by the integrity of the film sprocket reference edge used. The film transport I designed only uses the steel cam rider claw in tension to advance the film, the film gate is made of low friction acetal material so the force required to advance the film is low, so load on the cam is low and stepper motor shaft deflection is low. The eccentric circular cam running against the flat faced follower of the cam rider aperture generates a cosine velocity cam profile with its lowest rate of change of velocity as it approaches the Home position so no overshoot of film should occur. The cam stepper motor is rotated 360º for each film frame advanced so the motor’s constant magnetic properties for that step position should ensure the same Home position is reached every time.
Provided the video camera centre line height plus the video camera platform height, equal the film gate centre line height above the baseline, framing is easily adjusted. The 6 mm height of the film gate aperture allows at least 1 mm above and 1 mm below the image area of the film frame for the 0.1715 mm adjustment needed when setting or changing film formats.
System performance optimisation only became practicable after test and measurement methods were developed and included within the video capture and test software. Accurate timing of each stage of video frame capture: file storage, control communication delay and film advance. Measurement of overall video camera capture delay. Accurate measurement and collection of film frame to frame registration data to evaluate frame unsteadiness performance.
The speed of capture was found to be dependent on the specific model of video camera used, the type of shutter used in the video camera, global or rolling, the time taken to advance the film one frame, and the sustained HDD file writing performance of the Windows PC used for video capture.
Simple enough for the enthusiast to build? For the most part only simple tools and skills are required to assemble the parts and PIC kit. The manufacture of the acetal parts: film gate, cam, motor sledge, static axle, winding motor boss and film rollers requires model engineering facilities and skills. I made the cam rider claws for Mark 1 and 2 using hand tools. The cam rider claw for Mark 3 was laser cut from stainless steel and done commercially.
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