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Re: Eclair Cameras: Lens testing procedures

Lens testing procedures:

The best way to test lenses is to use a lens testing projector. It´s like a
slide projector with changeable lens mount. You fit your lens and project a
big images on a wall. Now you can see the quality of your lens, if it covers
super-16 and how many lines resolution. Most rental houses have this
projectors and it´s cheaper to let them test your lenses than shooting film
and pay for telecine time or film print.
You can´t evaluate the quality of a lens from a video monitor if you shall
use the lens for blow up to 35 mm film. The resolution on video NTSC or PAL
is to low.
For checking the cameras flange focal distance you use a depth-measuring
micrometer. The correct flange focal depth deepens on with lens mount you
use on your camera.  For Arri Baj. and PL the depth are 51.98 mm to the
gate. 52 mm to the ground glass.
For C-mount 17.526 mm, -0.02 to the gate.
Eclair baj. 48.00 mm. -0.02 to the gate.

You set the distance to the gate -0.02 mm shorter to get the light from the
lens in to the middle of the film emulsion. Green layer. The lens is set to
zero. For Arri 52 mm.

Take a look at this page, here you find the flange focal distance to most


Hans Hansson, FSF

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