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Re: [Rollei] Re: Shutters

At 06:53 AM 06/05/2002 -0400, you wrote:
>on 6/4/02 8:37 PM, Richard Knoppow at dickburk   wrote:
>> 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. 
>I'm sure the PQ-S shutters must have this problem as well, but it appears
>that Rollei has programmed the light meter system to allow for this.
>Exposure accuracy does not seem to vary with aperture as you would expect.
>These shutters achieve 1/1000 second through a combination of a special
>drive motor which produces more force than the one used in the regular
>shutter and shutter blades made from carbon fiber composite which have much
>lower mass than metal blades.
  The construction may be the answer. Its likely the opening and closing
times for this shutter are significantly faster than for conventional
shutters. This would increase the efficiency for larger stops and make
total open time more nearly equal to effective time at all stops. 
  The Graphic-1000 shutter used a construction which allowed the blade
drive mechanism to accelerate before starting to move the blades. This
shortened the opening and closing times, but the total open time is
1/500th. 1/1000 is the _effective_ time for the maximum shutter aperture,
meaning that an exposure at, say, f/22, would be a full stop greater than
one made at f/4.5.
  I don't have info on the Kodak-800 but revolving blade type shutters have
a theoretical limit of 50% efficiency at the greatest speed the mechanism
is capable of. The maximum marked  speed of the Kodak shutter may be lower
than the limiting speed, I don't know, but it would be easy enough to
measure if one had a working example. 
- ----
Richard Knoppow
Los Angeles, CA, USA