Hi Nathan,
I think that when the shutter is out of synch, it wouldn't work at all. I took all the care in the world to make an out-of-synch situation NOT happen.
I think that the tension of the spring is too low. I do not dare to increase it. I am afraid that the ribbons will not hold. I've used the ribbons of Aki Asahi. That ribbon is paperly thin.
Contax I v4, Jupiter 8M 50mm f/2, Tmax400.
Erik.
A couple of weeks ago I changed a set of ribbons in a II using Aki's ribbon material. At one point during my testing the shutter was capping, or there was variation in the slit, at the higher speeds. I found that this was because the clearance at the clutches was slightly too great. Not surprising given the replacement ribbon material is around half the thickness of the original. Very gently crimping them with a finger to close them remedied the incorrect gap. Essentially what was happening was that, instead of the first curtain running with the ribbons as it should at the faster speeds, the ribbons were slipping through the clutches, enabling the second curtain to catch up with the first.
But this was only the second Contax that I had changed the ribbons on, and as I was doing it for a friend who is going to use it (this is good, they should be used) I wanted the camera to be really reliable. Initially I was very conservative with the spring tensioning, wanting to apply the minimum amount needed to get the shutter to run correctly. Although it was running reasonably well, after adjusting the clutches it began to sometimes not latch up correctly, particularly when released upside down. You need to test the camera in various positions, I think, to be really sure it will continue to work, because sometimes gravity and friction may manifest certain problems only if a camera is fired in a particular orientation. The curtains would latch OK with the camera held normally, but upside down gravity began to brake the second curtain at the end of its run slightly, because it would cap the gate, but not quite latch fully. Another half a turn on the tensioner resolved these problems, and as it was still under five turns of tension on the adjuster I was satisfied with that.
I was, it is fair to say, pernickety with my testing, firing the camera across the speed ranges, checking and re-checking the shutter in various orientations again and again in the course of getting it right at all speeds in all positions. Without exaggeration, I would have fired it the best part of a thousand times, over a few days. I was working on a decent blister on my thumb by the end. Did I say I was pernickety? As far as durability is concerned. Only time will tell for sure, this is true. But my testing was getting on for thirty films worth of use.
I appreciate that the original has some design differences to the II, but you have used the same ribbons I did. So how much are you going to use your Contax, Erik? I would not worry about the ribbons. They may not last as long as Zeiss's original material, but be assured, they will last.
Cheers,
Brett
