[rollei_list] Re: "different types of black boxes" (was: OT / prove it !)

----- Original Message ----- 
From: "Nick Roberts" <nickbroberts@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Sunday, April 03, 2005 7:00 AM
Subject: [rollei_list] Re: "different types of black boxes" 
(was: OT / prove it !)


> --- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
>>
>>
>> -----Original Message-----
>> From: Nick Roberts <nickbroberts@xxxxxxxxxxx>
>> Sent: Apr 3, 2005 1:34 AM
>> To: rollei_list@xxxxxxxxxxxxx
>> Subject: [rollei_list] Re: "different types of black
>> boxes" (was: OT / prove it !)
>>
>>
>> But the Contax and Leica shutters did NOT have equal
>> performance. The Contax shutter was capable of
>> 1/1250
>> - the first FP Leica shutter managed 1/500, I think.
>> It is generally accepted that Leica lenses were
>> inferior to Zeiss until the mid-50s introduction of
>> rare earth glasses. In my personal experience, the
>> Jupiter 12 Biogon copy is every bit as good - and
>> faster - than my 35mm f3.5 Summaron - and that's a
>> pre-war design, manufactured under lower QC
>> conditions, against a 50's design. Mind you, the
>> Summaron is beautifully compact, and the Jupiter
>> doesn't fit on the Contax IIIa.
>>
>> Nick
>>
>>    The maximum speed is not really an issue. This
>> was a sales point only and Leica was able to
>> increase the top speed to 1/1000th easily. It is
>> also doubtful if the Contax shutter actually ran at
>> 1/1200th.
>
> Agreed, but my point was that the complicated design
> of the Contax shutter was to cope with the 1/1250
> issue - not required on the Leica shutter.
>
  I think you are assuming something that is not backed up 
by the evidence. I think the main reason Zeiss-Ikon used the 
Contax type shutter is that they had the design. While the 
Contax shutter is much more sophisticated than the Mirroflex 
shutter they both operate on the same idea of the gear train 
timer. I think the reason Leica did not have a 1/1000th 
speed on the earliest FP cameras is that with the slow film 
of the time no one would have used it much. Actually, the 
Leica design is well suited to fast shutter speeds as is 
proven by similar modern shutters with 1/2000th second 
speeds or even more. The main problem is the limit on the 
speed of the curtains due to their mass and the minimum slit 
width that can be used due to diffraction at the slit. For 
speeds higher than 1/1000 the speed of the curtains must be 
raised. This  is done in modern cameras. It also has the 
advantage that flash fill using strobe can be used at higher 
speeds because the highest speed at which the entire frame 
is exposed at once is greater.
  The fact is that the Leica type shutter acheives the same 
end as the Contax with far fewer parts and a much simpler 
design. The Contax shutter has little advantage other than 
running the short direction and that could be done using a 
Leica type shutter if the camera was shaped differently.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

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