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Eclair ACL More on the Strobing Camera


The strobing effect you are experiencing is due to the motor, rather than the camera. I assume you're running at 24fps? This problem seems to be more common with motors running at 24fps than 25fps. This is due to a slight uneven rotation of the motor, which is probably caused by the awkward inertia of the mirror (among other things). The mirror and shutter seem to reach a point where the power needed to clear the corner of the frame is different to that of the center. Hence you get a corner which is either over or under-exposed compared to the rest of the frame. Why this occurs more with 24fps than 25fps is anyone's guess, but telecine could also compound the problem.

The Cinema Products motor was developed with this in mind, and a flywheel was added to iron out these minor variations. They obviously isolated the problem, but I don't think even the flywheel solved it. Again, this problem doesn't occur with all ACLs so it would be interesting to hear what the serial number is. But as Eclair manufactured each camera to so many different tolerances, even this may not prove anything.

The only quick solution I could think around this problem would be a custom made shutter that could comensate for the uneven exposure in the corner. That would probably prove expensive. If you really get vexed I know an engineer here in England who would LOVE to get his hands on a camera like this, purely for the glory of solving the problem.



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