Synchro Compur shutter speed adjustment

[johnnyrod]

I am working on the small shutter on my Zeiss Contessa 35. It's going pretty well but I'm a bit bemused by the shutter timing settings; I thought I understood these from when I worked on an older Compur Rapid, but maybe I don't.

The shutter was really dirty. I followed some advice on here and split it, removed the blades, and flushed it with hexane. I followed the instructions on Retina Rescue as the M-sync has to be dismantled - great fun! I honestly can't believe how grubby it all was, but it's all back together, a little watch oil on the escapement (which stayed attached to the plate) and a little lithium grease for the main lever. It works fine and sounds nice and quiet.

I checked all the speeds, results as follows:
1 second=1.1 seconds
1/2s = 1/1.8
1/5=1/4.7
1/10=1/6.8
1/25=1/20
1/50=1/41
1/100=1/66
1/250=1/148
1/500=1/257 - these last two I am pretty happy with, and I don't think they can be adjusted anyway.

The hairspring looked about right when the retard lever was allowed to extend until it hit the inside of the shutter; I haven't adjusted it and the escapement hasn't been out so it hasn't lost its tension at any point. The spring for the retard was on the middle of three notches. I tried moving it back and forth, which seemed to make no difference to the faster times (1/25 and 1/100). I tried adjusting the retard end in (slower) and out again, but couldn't get 1/100 any faster than 1/66. It isn't so far off the 1/50 time and a long way from the 1/250 so I would like to adjust it up if possible. Actually the slow speeds were more accurate before I adjusted the retard end out:
1s=1.01s
1/5=1/5.1
but I only ran each once, and didn't check 1/2 or 1/10.

So, any advice please?
Thanks a lot

 

[rick oleson]

I'm not sure there is anything wrong with your speeds. In a leaf shutter, at the faster speeds the blades spend a lot of their 'open' time only partially open as they travel out and back in again. Therefore, to obtain the equivalent of 1/500 second effective speed takes about 1/250 second of partially-open time (and virtually zero fully open time). The blade travel time is less of a factor as you go down the speed scale, but it's still there. In your shutter, you're running 95% over at 500, 69% at 250 and 51% at 100, which does not sound too far off from what you would expect as compensation for blade travel time.

 

[farlymac]

I usually try to get a leaf shutter as close to one second as possible, and then I don't worry about the rest of the speeds. I figure if they are really off, then it will show on the film. With B&W film, there is plenty of latitude, and I've never noticed any problems.

PF

 

[citizen99]

+1 to the above postings. Also, if I measured timings on one of my shutters to find results as good as those in the original posting, I would be quite satisfied with it.

 

[Dan Daniel]

If you adjust the 1 second to be closer, other speeds will also get a bit faster. There are three adjustments- escapement position for 1 second, pin adjustment for 1/10 second, and the 1/500 adjustment. You can then adjust the cam to fine-tune each specific speed, but that's a bit silly all in all. Do them in order, 1 sec, 1/10 sec, 1/500, and accept the sloppiness.

 

[johnnyrod]

Thanks all. I think I was a bit spoilt by the first Compur (Rapid) shutter I worked on, as aside from the top speeds (with and without booster spring), the rest were really close, and the 1/100 I could even get from 1/80 to about 1/115 by adjustment, so I was perhaps a bit optimistic with this one. As said, these are pretty good, and the top two are pretty well as I've found on other 1950s/60s cameras, I just wondered about closing the gap. Just need to collimate it now and I can put a film in it!