[Konvas] A RUSSIAN 70mm camera

[Peter Haas]

On Apr 18, 2009, at 12:17 PM, Leo Vale wrote:

> ---It has a pulldown claw enter the perfs from the back of the  
> film. Totally unlike the eyemo/filmo movement which has the claw  
> enter from the front of the film, rides on a pin on the shutter.

Professional movements enter from behind.

The reason is the registration pins, which this camera apparently  
doesn't have, are more or less rigidly held from behind, thereby  
allowing for the entire aperture plate to be removed for checking and/ 
or installation of hard mattes.

The pressure plate assembly then does two functions: it provides back  
pressure, and it acts as a rigid locator for the registration pins.

The inside pin is always fully-fitting in both dimensions. For that  
reason it is called the "big pin".

The outside pin is always fully-fitting in the axial dimension, only.  
It is slightly narrower in the radial dimension, only. For that  
reason it is called the "little pin".

In this way, slight expansion or shrinkage in the media may be  
accommodated, while maintaining precise registration with respect to  
the "big bin".

The pull-down pins are usually narrower in both dimensions.

At least for 35mm, which has several perf types, this is one way to  
accommodate both BH (negative) and KS (positive) perfs.

Because of the long stroke required for 5-perf, a rear claw movement  
is preferable to a front claw movement.