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RE: [Rollei] Re: Shutters

At 02:51 PM 06/04/2002 -0700, you wrote:
>       So the Compur is more of a Audi? And the Copal the Lexus. 
>That leaves the Seiko to be a .... oh no ... Daihatsu.   Peter K   
>-----Original Message----- 
>From: curtiscr  ] 
>Sent: Tuesday, June 04, 2002 1:53 PM 
>To: rollei  
>Subject: Re: [Rollei] Re: Shutters  
>  > I'd say more like the difference between Subaru, Toyota and Mercedes! 
>> Bob     A professional  
>landscape photographer I know once told me he owned a kit of  
>  The outfit was stolen and  
>  He  
>thought the Fujinon lenses were sharper than the Schneiders, and -  
>in particular - he considered the Copal shutters to be superior in  
>  He refused to use Seiko shutters,  
>because they have a lever that flips back with a crash when the  
>shutter is released. 
>Curtis Croulet 
>Temecula, California    

   Keep in mind that Compur made many different models of shutters and that
most Compurs in service are getting old. 
   What is meant by "reliable"? Presumably, the two properties wanted in a
shutter are consistency and accuracy of speed. Its fairly easy to test for
both of these. My suggestion is the small shutter tester sold by Calumet
Photo for around $80 US. What this does not measure (although you can set
up to measure it) is shutter effeciency. Efficiency is the effective speed
taking into accound the opening and closing times of the blades. Most leaf
type shutters are marked according to the effective speed for the _maximum
aperture_ of the shutter. At smaller stops the efficiency goes up and the
effective speed goes down. At their top speeds Synchro-Compur shutters are
about 80% efficient. If you measure total open time the maximum speed will
read about 20% low, maybe more. 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. 
  Compur shutters are notably trouble free if kept reasonably clean. By
reasonably clean I mean having the shutter properly serviced at intervals
by someone who knows what they are doing. A shutter probably does not need
a CLA more than about onece every five years, and maybe not that often. 
 I don't know Copal shutters as intimately as Compurs. They could very well
be improved over the Compur but someone who had both could tell by using a
shutter tester with some sophistication about what its testing. 
  As far as mechanical stability, i.e., holding the lens cells in place, I
doubt if there is much, if any, difference. 
  There are other good shutters beside the Compur. Kodak Supermatics, if
clean and with good main spring, are quite accurate (they were hand
adjusted) and very consistent. They are also very rugged. 
  Gauthier, (sp?) who made Prontor shutters, mainly made low cost shutters
for cheaper versions of folding cameras. These were mostly single action
(self cocking) shutters with limited speed ranges. Its interesting that
this is the line which survived. 
  BTW, the term "press shutter" for a self-cocking shutter is of very
recent origen. In the past a press shutter was one which included a
press-focus device, sometimes called a blade arrestor. This holds the
shutter blades open for ground glass focusing without having to use the T
setting. Compur press shutters also had oversize buttons on the cocking
lever. On these shutters the blade arrestor replaced the self-timer found
in the standard version. 
  No press camera would have employed a self-cocking shutter since they are
generally without the highest speeds and require strong pressure on the
triping lever (since you are also cocking the shutter). They would have
been useless with the old type of solenoid flash synchronizer. 
  I think the term is used for self-cocking shutters due to a
mis-understanding of its original meaning by Japanese or Asian manufacturers. 
  While some very good lenses are now found in self-setting shutters in the
past they were always the mark of a cheap camera, except for very large
shutters (Ilex Universal #5). They still have the same shortcomings they
always had, namely limited available motor power. Since the cocking is done
when the shutter is tripped the tripping lever must necessarily have a
relatively long travel and be hard to move compared to one which is simply
releasing stored energy. 
- ----
Richard Knoppow
Los Angeles, CA, USA