Weird 35mm lens adapters

Vultch

Vultch

Well-known member
I remember seeing these Frankenstein lens adapters at cameras and electronics shows, the type that allowed a Sony EX1 to be mated with a 35mm lens, now the things were huge but what really intrigued me me was the fact that there was a spinning piece of glass in the device. A motor driving an optical disc that spun around.
I never really got an explanation of why this thing had to be spun.

I can understand mating one lens to another and the problems contained therein, but why the spinning disc?

Anybody remember these things.
 
If the disc was not spinning the pattern on the ground glass element would be seen. There were a few static adapters as well that did not have spinning, or vibrating elements, but they were in the minority.
 
The disc that was spun (or vibrated) was the ground glass. The 35mm lens projects an image circle onto the ground glass which was then recorded using the camera's original lens and 1/3" sensor. In order for the ground glass to "hold" an image it had to be course enough. Too transparent and the image would not be projected on the ground glass and too opaque or course and not enough light transmission would occur causing a loss in light. Sanding down ground glass using a specific grit to the right amount was always the art to 35mm adapters. In order to avoid static grit/ground glass pattern appearing in the resulting footage, spinning or vibrating was necessary to blur, or at the least vary, the ground glass pattern.
 
Loved our Letus adapter we had mated to our XHA1, I still have a few projects in our portfolio that were shot with that rig. Very "film like" look.
 
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