Holding up the PL mount to compare it to the BNCR mount on the Mitchell 205

Mitchell 205 to PL mount Conversion?

At first glance, it seemed possible that the Mitchell 205 could be relatively easily converted for PL lens mounts. This would make the camera more versatile as there are more lenses available in PL mount than in BNCR mount. So I began the process of taking the camera apart to find out if the conversion is possible. What I discovered as I disassembled the camera are a number of ingenious modifications. Mitchell NC and BNC cameras both feature variable focal plane shutters, which was a feature cinematographers really liked. Several of the contemporary reflex conversions eliminated the variable shutter in order to accommodate the spinning mirror reflex mechanism.

In some of the 205 cameras, they were able to add the spinning mirror reflex mechanism and preserve the variable focal plane shutter. To accommodate both of these mechanisms, they had to carve away much of the camera casting and aperture plate to allow the spinning mirror to get close enough to the film plane so it could relay the entire taking lens light bundle to the viewfinder without vignetting. Because so much of the aperture plate was machined away, a ground and polished metal bar was added to the film side of the aperture plate as a reinforcement. The ground glass was mounted in an assembly that allowed it to swing out of the path of the aperture plate so the aperture plate could be removed for cleaning. All in all, several ingenious modifications to keep the old with the new.

The many hours investigating this showed me that there simply isn’t enough material to machine a new mounting surface for a PL mount without interfering with the spinning mirror and compromising the integrity of the camera’s main casting. Sadly, my conclusion is that a PL mount conversion is not practical with this camera.