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Re: [Rollei] 220 film in 'ordinary' Rolleiflexes

At 12:19 PM 09/02/2001 +0200, you wrote:
>I took a deep breath and decided to challenge you there, Mr. Knoppow.
>a) The purpose of the shifting pressure plate is not to make room for 
>the Rolleikin lever. It DOES make room for the lever but the purpose is 
>to position the plate differently, i.e. closer to the camera. If the 
>sole purpose of the shifting mechanism was to make room for the lever 
>it would have been far easier to make the cutout in the plate a little 
>longer. The intention to make that cutout just as long as it is, 
>obviously was to make it impossible to close the back with the plate 
>wrongly set to 6x6 (as previously described). 
>b) There certainly is a 'film channel' in the Rolleiflex and the 
>so-called pressure plate does NOT go flat against the sides of the 
>aperture (and it always stays well clear of the guide rollers). When 
>the back is closed there remains a definite gap between pressure plate 
>and camera body (the sides of the film aperture). The size of the gap 
>is controlled by the position of the plate. You can work out what size 
>the gap approximately has with calliper and ruler. I found that with 
>the Rolleikin fitted it is something like 1/100 of an inch between 
>plate and Rolleikin (35mm film definitely is thinner).  
>In the 6x6 position it is more than 2/100 of an inch between plate and 
>body aperture sides (surprisingly, as film and backing paper together 
>are not much more than 1/100 inch). So there is nothing like 'the film 
>lifting the pressure plate' but the film running in a gap (a channel) 
>of exact dimensions. Otherwise, with the film squeezed between plate 
>and body aperture sides it should be impossible to transport the film 
>at all. 
>Sven Keller
>> I think this has already been addressed. The purpose of 
>> the shifting 
>> pressure plate is to clear the release lever of the 
>> Rolleikin. If you close 
>> the back with the plate in the 6x6 position the release 
>> lever pushes the 
>> plate away from the film causing blured focus. You will 
>> also find you can't 
>> wind the film because the release lever can't operate.  
>> There is no "film 
>> channel" in the Rollei, the pressure plate goes flat 
>> against the sides of 
>> the film aperture and guide rollers. The film lifts it 
>> away somewhat so it 
>> presses the film against the guides at the  sides of the 
>> aperture and 
>> against the top and bottom rollers (for roll film). The 
>> Rolleikin becomes 
>> the film gate or aperture when it is installed, with its 
>> own guides. Since 
>> the film lifts the pressure plate away from the focal 
>> plane it is also 
>> lifted off the 6x6 side guides by the film which is 
>> pressed against the 
>> 35mm guides on the Rolleikin adaptor. The guides extend 
>> well beyond the 
>> aperture assuring control of film flatness at the ends of 
>> the frame.  
>>   The Rolleikin is about as elegant a makeshift as you 
>> are likely to find.  
>> ----
>> Richard Knoppow
>> Los Angeles,Ca.
>> dickburk  
   This post caused me to make a very close examination of the whole film
gate arrangement in a Rolleiflex and Rolleicord. Sven is right and its
cleverly done. At each side of the back plate there are two little legs
sticking out. When in the 6x6 position these contact bosses next to the
film gate. On the Rollei IV one of them has the red dot on it. These hold
the back plate in position controlling its spacing. When in the 35mm
position the legs on the back plate contact the surface just under the
bosses reducing the clearance by the thickness of the bosses. I haven't
tried to measure the clearance but will trust Sven's measurements for the
moment. The back plate is also undercut along the lines of the film
reference surfaces on both the 6x6 aperture and Rolleikin aperture. I think
I understand the mechanism used to keep the film flat but need to visualize
it a little better. 
  When I got this message I was going to suggest that Sven open up a camera
and have a look and then thought maybe I had better do it first. When I
made my first post I hadn't noticed the little legs, or rather, didn't
understand their significance.
  I'm glad Sven challenged my version of how the back works because
otherwise I would not have seen this very clever arrangement. 
  I wonder if any of this is covered by US patents. Unfortunately, the on
line patents at the U.S. Patent and Trade Mark Office do not allow
searching for other than patent numbers for patents issued before about
- ----
Richard Knoppow
Los Angeles,Ca.