Sega
Established
Just used this, thank you for the how to.
HOW TO: FED & Zorki Curtain tension.
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farlymac
PF McFarland
It never ceases to amaze me how little one needs to turn the adjustment screws on the shutter curtains. And how many times you have to do it until you can get the locking collar in the right position to insert the locking screw. But I persevered yesterday and got my Zorki-4 running smoothly again.
PF
PF
NorpA
Established
Thank you so much for the detailed instructions! Even after all these years, they are still incredibly relevant and helpful. I followed the steps diligently, and now my once completely stuck shutter plane is back to its fully functional state. I'm beyond grateful!
Now, I do have a question for the experts out there. While I understand the ultimate goal is to have parallel curtains despite any angulation, I'm curious about the necessary steps to achieve perfectly parallel and straight curtains. Any guidance on this would be greatly appreciated!
Here my restored Pentax S1a - 1/1000
I calibrated the curtains to have a travel speed of 16.5 ms over 36mm
The expected exposed area should have 2.18 mm width, in the picture below I measured ~2.5 mm
PS. Here's a useful tip to share! Instead of capturing the image below using a CRT, I simply utilized the handy feature "slow motion" available on smartphones nowadays. It worked like a charm!
Now, I do have a question for the experts out there. While I understand the ultimate goal is to have parallel curtains despite any angulation, I'm curious about the necessary steps to achieve perfectly parallel and straight curtains. Any guidance on this would be greatly appreciated!
Here my restored Pentax S1a - 1/1000
I calibrated the curtains to have a travel speed of 16.5 ms over 36mm
The expected exposed area should have 2.18 mm width, in the picture below I measured ~2.5 mm
PS. Here's a useful tip to share! Instead of capturing the image below using a CRT, I simply utilized the handy feature "slow motion" available on smartphones nowadays. It worked like a charm!
NorpA
Established
I have just realized this question is not correct, most probably the diagonal depends on how the image is acquired by the registering camera
fabiolanotte
Newbie
I just used this instruction and now the frame exposure on my FED-2 is perfect. Thank you for having provided it! 🔝
KoNickon
Nick Merritt
THIS is the real pain in the neck with this adjustment -- not really discussed in this string before this note. The locking screw holds the locknut in place to keep it from backing off. But the locknut has only 2 or 4 (depending on the camera) positions -- cutouts -- that enable you to reinstall the locking screw. The locknut, as I understand it, is threaded and itself needs to be tightened down once you get the adjustment screw into the correct position. But how do you keep the adjustment screw in the correct position while you get the locknut tightened down, and the locknut properly aligned do you can reinstall the locking screw?
It seems like the locknut is somehow threaded with the adjustment screw, thus effectively interfering with the correct setting of the adjustment screw. And then you may still have the locknut incorrectly aligned with the hole for the locking screw.
I've tried doing this once -- probably jumped in too rashly -- and managed to mess up a Zorki 6. Hopefully not irreparably! But I simply was unable to successfully coordinate all these with the two hands I was born with.
But I'm right now studying a Zorki-2 that seems to suffer from the condition described way back in post #2 of this thread: "If it starts (from the right) through a much darker area, or both curtains travel without a gap between them, then you may have a problem in the release mechanism." OK, I'm all ears -- any guidance on this? It's intermittent with mine, and seems to only affect certain shutter speeds -- 1/250 mainly.
farlymac
PF McFarland
The way I approach adjusting the Zorki/FED shutter curtains is the first adjustment is always going to be wrong no matter what. But it gives you an idea of which direction you need to go towards achieving the proper balance of getting the spool locking collar tightened and the locking screw installed. Sometimes you need to go beyond where you think the adjustment point should be because by the time you button everything up it will then settle at the proper speed. It mostly has to do with the torque of the locking collar on the spool. As for a proper tool to do the job I've thought of taking a mini-open-end wrench and bending the tips to fit the locking collar slots. But since I don't work on cameras as much as I used to, I just use a pair of skinny long-nose pliers.
As for the release problem you have, I'm thinking a weak catch lever spring could be the culprit. But since you say it mostly happens at one speed, maybe the speed dial mechanism has been damaged from improper usage procedure.
PF
KoNickon
Nick Merritt
Thanks, Phil, you more or less confirmed what I thought, that it is a PITA!
I did the cathode ray tube test described farther up in the thread and the spacing (i.e. the width of the slits) looks consistent, so no problems with capping/tapering that I can see. So I don't think I need to mess with the shutter curtains. Whether the speeds vary properly, I'd need to study more closely, but they look and sound right.
"Weak catch lever spring" -- I guess to look into that more closely. I wouldn't say it's just one speed -- but 1/250 seems most prone to it.
I did the cathode ray tube test described farther up in the thread and the spacing (i.e. the width of the slits) looks consistent, so no problems with capping/tapering that I can see. So I don't think I need to mess with the shutter curtains. Whether the speeds vary properly, I'd need to study more closely, but they look and sound right.
"Weak catch lever spring" -- I guess to look into that more closely. I wouldn't say it's just one speed -- but 1/250 seems most prone to it.
farlymac
PF McFarland
It's just a guess on the spring as I've never taken the speed control apart before.
PF
felixm6
Newbie
FSU rangefinders are rarlely subjected to rigorous (electronic) shutter testing. Such testing equipment used to be very expensive and not even all repair shops would have had such a device. Nowadays, however, one can easily build an Arduino-based tester with a laser emitter and sensor which will test reliably up to 1/500 (and with some care even 1/1000). Recently I built such a tester and the moment of truth had arrived. My Nikons, Leicas and Japanese Leica clones were found to be all well within the tolerances. But my FSU rangefinders (about a dozen) are seriously out of wack. To be sure, I am not talking about junk box items. I had given all of them a full CLA, at times down to the last screw and including curtain changes. I had regulated the speeds by visual inspection. They seemed to, and sort of did operate just fine: smooth shutter operation, speeds roughly correct, no capping, rangefinder and flange distance correctly adjusted. However, the shutter tester revealed: The exposure at 1/100 and shorter is unbalanced. ANSI allows half a stop of difference between the opening and closing speed. All of my specimens were well off the norm, some approximating a full stop at some speeds. (Depending on the subject of a photo you may not notice that, if you don't look for it.) What's worse, no matter how I now tweaked the curtain tension, there was just no way to meet the tolerance of 1/2 stop across all speeds. Beyond certain points the rollers simply refuse to translate tension into speed. (A Leica or, say, an LTM Canon is very responsive to even a quarter turn.) I conclude that FSU cameras were always designed for rougher tolerances and one should not hope that they can be adjusted to the specs of German or Japanese cameras.
santino
FSU gear head
Yeah, but who cares? I’m not going to expose a 25 Euros slide film with a 30 Euros camera anyways… and it is definitely good enough for negative film (be it bw or color).
JeffS7444
Well-known
Mechanical shutter error easily exceeds +/- 0.5 stops even for the most expensive cameras, and a full stop or more wouldn't be uncommon: It was either Popular or Modern Photo which used to publish shutter speed graphs as part of their lab reports.
IME, factory-recommended shutter tension is plenty adequate when all is else is in good working order, and this includes shutter curtains: Brand-new rubberized silk is extremely supple, but the stuff I pull out of Khrushchev-era Soviet cameras tends to be kinda stale, even though it may appear intact and free from pinholes.
IME, factory-recommended shutter tension is plenty adequate when all is else is in good working order, and this includes shutter curtains: Brand-new rubberized silk is extremely supple, but the stuff I pull out of Khrushchev-era Soviet cameras tends to be kinda stale, even though it may appear intact and free from pinholes.
mhw
Newbie
I wanted to second this observation. I recently serviced a few FSU rangefinders and could not get any of the shutters to be precise by tuning the two curtain tension springs, even after a full disassembly and lubrication. The speeds are uneven and easily over half a stop off. Besides replacing components and hoping for the best, I am not aware of any additional steps that may improve the precision.
WoodallP
Pragmatist Barnack lover
To be honest, a good methodology on shutter tensioning for Leicas and copies would be appreciated by all. As a physicist, I sometimes wonder how the system can work at all; but it does apparently!
Valkir1987
Well-known
You can read more about the cause here:
The fatal flaw in the Soviet Leica shutter
The difference is not noticeable on most films, and the error can be solved by some workshops. I have a few Zenit cameras that do equal exposure across the frame. Early Fed cameras don’t have this problem, they started coupling the curtains from the 1g and onwards.
The fatal flaw in the Soviet Leica shutter
The difference is not noticeable on most films, and the error can be solved by some workshops. I have a few Zenit cameras that do equal exposure across the frame. Early Fed cameras don’t have this problem, they started coupling the curtains from the 1g and onwards.
mhw
Newbie
Very interesting read! I checked some of my FSU rangefinders with uneven exposure, and the overlap between the two curtains indeed changes with the curtain positions. I don't know if this phenomenon explains the uneven exposure on my cameras though. For speeds faster than 1/100, the shutter button/right side is always exposed for +0.5 stop or worse. It's as if the second curtain takes too long to start moving. On the other hand, the exposure on the unused film/left side can be made fairly accurate with spring tension adjustments.
Valkir1987
Well-known
The shutter speed tester is both my friend and enemy. The most likely reason for FSU cameras to have the shutter blinds coupled is the fact that they keep working within a certain tolerance when the spring tension changes and the lubrication dries out. 1/500th and 1/60th do even exposure on most of my cameras. It's the 1/125 and 1/250th speed that have the most unevenness. You can work around these speeds when equal exposure is required, (landscapes for example)
My approach is to set the second curtain first on a swift closing speed, without putting to much tension on the spring and the release hook. I adjust the tension of the first curtain until the unevenness is minimal.
A common misconception or paradox is the fact that the second curtain needs to be slower than the first. They do not run at a constant speed, but they accelerate. The acceleration for both curtains should be the same and causes the slit between the curtains to become larger at the end of the frame. (the time of the curtains passing a certain point should of course be the same)
My approach is to set the second curtain first on a swift closing speed, without putting to much tension on the spring and the release hook. I adjust the tension of the first curtain until the unevenness is minimal.
A common misconception or paradox is the fact that the second curtain needs to be slower than the first. They do not run at a constant speed, but they accelerate. The acceleration for both curtains should be the same and causes the slit between the curtains to become larger at the end of the frame. (the time of the curtains passing a certain point should of course be the same)
WoodallP
Pragmatist Barnack lover
How true! Never measure a shutter speed just to know. It is the road to perpetual disappointment 🙂
A great point well made and often misunderstood!
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