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Dmcrite33
Tinkerer
Username: Dmcrite33
Post Number: 9
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 03:15 am: | 
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I was quite surprised, while disassemblying a Prontor-SVS shutter on a Paxette to find an extra shutter blade. There are 5 in this shutter, but I found 6!!. Evidently 2 were stuck together during assembly. The shutter evidently worked properly(?)for a number of years. I wonder how many times this has happened... |
Donnie_strickland
Tinkerer
Username: Donnie_strickland
Post Number: 68
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 07:13 am: |
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I don't think that was a mistake. Many Prontors, of different models, did indeed have an "extra" sixth blade. |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 159
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 02:58 pm: |
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Absolutely right, Donnie. Both my Super Paxettes had 6-bladed shutters, though to the best of my recollection my Paxette IIM had a 5-bladed one.
The shape of the blades is different on the 5 and 6-bladed units, and I think the idea of the extra blade is to reduce the likelyhood of a light leak at the point where the sequence of blades starts and ends. |
Markus
Tinkerer
Username: Markus
Post Number: 117
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 04:58 pm: |
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I have seen this in Seikosha shutters as well. This isn't a case of two blades stuck together, though. Instead, when you reassemble, put the sixth blade on top of the first blade that was put on (with the other four sandwiched between the first and the last, when the shutter is closed). |
Dmcrite33
Tinkerer
Username: Dmcrite33
Post Number: 10
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 07:21 pm: |
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Whatever... I am not convinced this extra blade was not a slip by the assembler. I have yet to see a Prontor shutter, although I by no means have seen them all, that had one blade directly on top of another on the same pivot post. It serves no purpose. I set aside the extra blade on this shutter and it performs perfectly with the five. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 872
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 29, 2009 - 08:21 pm: |
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It's not the most common practice, but it was probably not a mistake, especially when it's been confirmed in other Paxettes. The Argus C4 also had a 6th blade. It would not have been directly on top of the other blade on its pivot, though, they would be stacked in sequence so that the double blade has one at the top and the other at the bottom of the 6-blade stack. Its purpose, I expect, was as an extra shield against light leaking past the blades ... |
Dmcrite33
Tinkerer
Username: Dmcrite33
Post Number: 11
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 30, 2009 - 05:10 am: |
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But I would suspect that this is not so much a Paxette issue as it is a Prontor issue. This shutter was used on several cameras. And I can see no benefit by your explanation of an extra shield against light. But... you may be right. Cheers... |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 160
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 01, 2009 - 03:03 am: |
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Which model of Paxette are you dealing with, Dmcrite33? Personally, I've only seen this 6th blade on the Super Paxette. Every other Prontor I've met has had 5 blades. As far as I can remember the 6th blade was fitted in the same way as the Argus C4 Rick describes. There was something different at the relevant pivot-point which enabled the extra blade to exist, but it was over 5 years ago, and before I started keeping careful notes. I'm still having a hard time believing that it would be possible to fit 6 blades in a 5-blade shutter! My explanation for the 6th blade goes as follows: -
Prontor or Braun decided to modify the shape of the shutter blades to improve the opening/closing speed. The resulting slimmer shape was OK where one blade is in direct contact with the next, but due to the way that a diaphragm shutter has to be assembled, like a spiral staircase, there is always going to be a larger clearance between the first and last blade in the sequence. This may have proved to be a potential light leak with the new blade shape. The 6th blade prevents this by increasing the overlap between the first and last blades.
This may well be total fiction, but it works for me! |
