Curtain Travel Time

[limnidytis]

Does anyone know the spec for the curtain travel time in Zorki/FED cameras? The specification would greatly help in adjusting the shutter tension. I tried Google, but couldn't find travel time specifications for any focal plane shutter.
Thanks

 

[goamules]

...........

 

[fidget]

Interesting thought. How would it help you? (and, how would you measure it?)

 

[wolves3012]

On the basis that the later models have flash-sync speeds of 1/30th second and that, at that speed, the curtains are fully open, it must be something approximately that time. Possibly slower on earlier models with 1/20th. I've never seen an actual spec, if there ever was one published.

It's more important that the two curtains run at the same speed, with no tapering or capping than to get an exact curtain travel-time. Actually, with a correctly lubricated shutter, it's hard to get it (badly) wrong.

 

[limnidytis]

Why would I measure travel time

Why would I measure travel time

There are instruments to measure the travel time for the 1st and 2nd curtain. Travel time is the same regardless of shutter speed. I have one of the devices and have measured travel times in my SLR cameras - both with metal blades and cloth shutters. No surprise, the 2nd curtain is always somewhat slower than the 1st. I've not been able dig up any specs for any camera - but I'm sure they exist for later SLR cameras. I don't know if such a spec ever existed for early FED/Zorki/Leica cameras. It would be nice to have a spec or some idea of correct travel time. In the absence of a spec, I can guess. I'm sure that someone, somewhere has measured this before.

 

[Roger Hicks]

There are instruments to measure the travel time for the 1st and 2nd curtain. Travel time is the same regardless of shutter speed. I have one of the devices and have measured travel times in my SLR cameras - both with metal blades and cloth shutters. No surprise, the 2nd curtain is always somewhat slower than the 1st. I've not been able dig up any specs for any camera - but I'm sure they exist for later SLR cameras. I don't know if such a spec ever existed for early FED/Zorki/Leica cameras. It would be nice to have a spec or some idea of correct travel time. In the absence of a spec, I can guess. I'm sure that someone, somewhere has measured this before.

Possibly -- but equally, maybe it was just a question of 'the best we can do', in which case there might be little or no advantage in measuring.

And, of course, there are shutters in which both slit width and tension (curtain speed) are adjusted, even in 35mm (Contax/Kiev).

Like you, I'd be intrigued to know. I just question whether the designers thought in terms beyond 'the best we can do'.

Cheers,

R.

 

[colyn]

Are you wanting to know the approx shutter velocity?

If so the time from shutter release till the curtains are at the rest position in Leicas is 1/20th second for models that have 1/20th on the top dial and 1/30th for models with 1/30th. Both curtains have to travel at the same velocity to prevent capping (closing curtain catching up or passing the opening curtain). I would assume the same for Fed's and Zorki's. The Contax models have a slower shutter velocity.

However this velocity does not set actual shutter speed. That is determined by the width of the slit between the opening and closing curtains which is maintained by matching velocity of both curtains. This is done with a shutter speed tester. You first set initial spring tension on both opening and closing curtains. Then you place the shutter tester eye in the center of the film gate and adjust the opening curtain tension to get 1/500th within tolorances. Then you measure the curtain velocity near the opening side of the film gate then moving it to the closing side and adjust opening curtain tension to match the closing curtain's velocity. This additional tension will not change the speed you just adjusted unless you have to apply more than 1 to 1 1/2 turns.

The opening curtain has to trigger several vital operations and as such has more spring tension. The closing curtain which has less tension only has to close the curtain.

In most cases the closing curtain tension is set first to a set number of turns such as 1 3/4 turns on the Leica and no additional adjustment is needed. The opening curtain tension is then set to match the closing curtain velocity. I suspect the Fed and Zorki will need more tension since they use a heavier curtain material than the Leica.