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RE: [Rollei] Re: Shutters

At 07:34 PM 06/04/2002 -0400, you wrote:
>At 03:43 PM 6/4/02 -0700, Richard Knoppow wrote:
>>Because the opening and closing times are
>>determined by frictional and inertial forces its hard to reduce them
>>without the use of special materials or the use of an oversize motor to
>>drive the shutter. The latter increases the stress on everything it moves.
>>Very few attempts to make conventional shutters with speeds greater than
>>about 1/500th second have been made.  Both the Graphic 1000 and Kodak
>>Synchro-800 proved to be short lived in service because of the concentrated
>>stress on some parts. 
>The East German Presto shutters, made at the Carl Zeiss Jena Saalfeld plant
>(also home to OAS, incidentally) had a top speed of 1/750".  These were
>used for more than a decade in the Werra line of 35mm cameras and proved
>very hardy in use.  But, again, these are 00 shutters, small by
>leaf-shutter standards.
>msmall    FAX:  +276/343-7315
>Cha robh bàs fir gun ghràs fir!
 I wonder how these were made. There have been a number of shutter designs
using double shutter blades which turn continuously when the shutter is
operated. In the US the Wollensak Optimo and Kodak Rapid-800 are examples
of the type. Higher speeds can be obtained from this design than from
conventional reciprocating blade shutters but the efficiency at the top
speed is only fifty percent, and, of course, varies with the aperture.
Actually, this is a problem with all high speed, low efficiency shutters,
the effective exposure time varies with the stop size, becoming longer for
smaller stops. 
- ----
Richard Knoppow
Los Angeles, CA, USA