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Werner J. Becker
Tinkerer
Username: Wernerjb
Post Number: 18
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 24, 2006 - 05:26 am: | 
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I have a CZJ 2,8/50 Tessar in M42 mount that I occasionally use as a manually operated lens on a Minolta SLR via Practica mount adaptor. Everything is fine except for one thing: the aperture is the auto click-stop type, but as soon as you stop pushing the lever outside the lens barrel it returns to full opening. In other words, the lens cannot be permanently stopped down manually, so the aperture lever has to be pushed whenever you want to take a picture. On Exacta lenses I use the same way (by means of the "E- adaptor") it is possible to keep them stopped down. Is this Tessar different in that respect ? |
Glenn Middleton
Tinkerer
Username: Glenn
Post Number: 27
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 24, 2006 - 08:47 pm: |
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You have to modify the lens or the mount adapter, so that the actuating pin is held in all the time.Lens can only be used stopped down.
Easiest way is to attach a ring of metal to bottom of mount threads in the adapter. As you screw in lens, the pin bears on the ring and is pushed in - closing aperture. You can also drill and tap the rear of the lens to take a small grub screw. This is used to lock the pin in the aperture closed position.
Some third party mount adapters have the ring machined in place when they are being turned up. |
Werner J. Becker
Tinkerer
Username: Wernerjb
Post Number: 19
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 28, 2006 - 12:50 pm: |
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Thanks a lot, problem solved! |
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