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Vinzenz
Tinkerer
Username: Vinzenz
Post Number: 41
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 10:50 am: | 
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When using a Leaf Aptus-II 6 on a Hasselblad 500C/M everything worked fine with fast shutter speeds, but slow speeds below 1/15s created streaks in the pictures.
This is a known issue, if the pc sync of the lens needs repair, according to Leaf. The digital back is wired to the pc sync of the lens. If the digital back starts processing the file while the shutter is still open, you get the result pictured below.
Does the metal switch for the flash sync in the Compur shutter maintain contact for the whole time the shutter is open or only initially when the shutter opens? I have cleaned many Compurs, but never paid enough attention to the flash contact...
How should I clean/repair the pc synch (Planar 80mm f2.8, S-Planar 120mm f5.6, the Distagon 50mm f4 works fine)? Is this just a matter of bad contact between the inner and outer shell of the sync port? Or do I need to take apart the lens? I could start bending the cable's jack a little, but I thought I would ask here first.
Thanks for any comments.
Vinzenz
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Brcamera
Tinkerer
Username: Brcamera
Post Number: 23
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 11:20 am: |
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I have no experience with the Leaf back, but lots with the Hasselblad shutter-the sync contacts on the Compur shutter open as soon as the blades reach full open position and the contacts remain closed until the blades close. So with a slow exposure, say one second, the sync contacts are open the whole one second. |
Vinzenz
Tinkerer
Username: Vinzenz
Post Number: 42
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 02:15 pm: |
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Can the flash contact be out of sync, i.e. release the contact before the shutter blades are closing? I was told that this causes the strange images.
How could I resync such a shutter? Is the contact corroded from usage? Do I have to replace the contacts or is it a matter of cleaning/adjusting?
All the shutter speeds are fine down to 1sec. The blades open and close snappy. The lenses perform fine with film. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 24
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 02:27 pm: |
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You can check the flash sync easily by firing a strobe through the front of the lens while looking through the back of the camera. You should see a full flash of light. I do assume you are set for X sync? |
Vinzenz
Tinkerer
Username: Vinzenz
Post Number: 44
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 03:32 pm: |
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Thanks for your comments, Brcamera.
Testing with flash works, of course. However, I cannot check for how long the flash sync keeps the contacts closed, because the flash duration is far shorter than shutter speeds below 1/15 and there is obviously no synchronisation on the ''second curtain''/closing shutter with the Compur.
The problem is that the digital back gets the signal for the duration of the capture from the flash sync port. It captures an image for as long as the flash contact is closed. When the sync releases contact, the back starts processing the image. If the shutter is still open at that time, it will corrupt the file. I have to make sure that the flash sync remains closed for the exact time of the selected shutter speed. Maybe you could explain how the flash contact can open again before the shutter blades close?
It seems that with two of my lenses the sync cannot maintain a closed circuit for longer than about 1/30. With slower speeds the back starts processing while the shutter is still open. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 25
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 03:57 pm: |
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Well, the contacts can not open until the blades start closing, there is a part in the shutter that holds the contacts closed when the blades are open. I don't have experience with the digital back to know how this timing issue for slow speeds is worked around.
Bill |
Vinzenz
Tinkerer
Username: Vinzenz
Post Number: 45
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 04:29 pm: |
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Thanks a lot for the explanation. That makes the answer I got from Leaf not very convincing. I have read somewhere that the contacts can wear out from use. However, the shorter speeds work fine. I will try to gather more information about this tomorrow. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 26
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 07, 2010 - 06:28 pm: |
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Well, I have replaced a lot of Hasselblad sync contacts but the symptom is normally a flash that does not fire at all! |
Glenn
Tinkerer
Username: Glenn
Post Number: 847
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 08, 2010 - 06:42 pm: |
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Make yourself a simple test device using an old flash lead, a torch bulb and a 1.5 volt battery. This will allow you to view the actual contact dwell through the lens - the bulb will remain lit whilst the contacts are closed. |
Vinzenz
Tinkerer
Username: Vinzenz
Post Number: 46
Registered: 06-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 09, 2010 - 11:58 am: |
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Quite an ingenious idea and so simple! Thanks Glenn |
