HOW TO: FED & Zorki Curtain tension.

[oftheherd]

Originally Posted by fidget

Just recently I have been hit by minor GAS and have acquired a few M42 cloth shuttered SLR bodies. Zenit, Fujica ST605, ST705, Cosina CSR, CSM (there may be more on the way!)
The preliminary checks that are described at the beginning of this tutorial are relevant to these shutters as well, although the mechanics of adjustment is obviously not the same.

Performing these simple checks has shown a sticking 2nd shutter curtain on one and fairly serious fade as the curtains slow whilst travelling. Seeing these has helped to avoid the disappointment that the first test films would have brought. It is, of course, no surprise that 30-odd year old SLR bodies may need a service to rectify these points...

Look forward to a tutorial on the Fujica SLR's (if needed). My ST 801 and 901 cameras are fine so far, but one never knows. Fujica made cameras apparently to a pretty high standard. I think they intended to break into the pro market, but didn't market well as such. By the time they decided on a bayonet mount, I don't think they had kept up with the quality control. Maybe they just moved too fast. Their AX3 seems to have held up well though.

[fidget]

Originally Posted by oftheherd

Look forward to a tutorial on the Fujica SLR's (if needed). My ST 801 and 901 cameras are fine so far, but one never knows. Fujica made cameras apparently to a pretty high standard. I think they intended to break into the pro market, but didn't market well as such. By the time they decided on a bayonet mount, I don't think they had kept up with the quality control. Maybe they just moved too fast. Their AX3 seems to have held up well though.

Yes, I too would like to see instructions on how to service these and solve elementary problems. I just love the feel of the Fujicas. A quick reccy under the base cover really put me off having a go.
Now my 35mm gear repair efforts are going on hold for a year whilst I get some use out of the gear (MF mainly) that does work. Got to get back on track, piccies not cameras.....

[fidget]

Originally Posted by mynameislee2

Hi,

My curtains need adjusting but this technique relies on a CRT monitor or TV. I have neither, all the monitors and TV's in my house are flat screen. I'll probably venture over to my parents as they aren't quite as up to date .

Is there an alternative way of checking without a CRT?

Regards,
Lee

Hi Lee,
I guess that at one time everyone had access to a scanning screen of some description. Perhaps there are other ways of doing this. A trip to yesterworld may be in order....good luck...

[rxmd]

Hi Leea,

Originally Posted by mynameislee2

My curtains need adjusting but this technique relies on a CRT monitor or TV. I have neither, all the monitors and TV's in my house are flat screen. I'll probably venture over to my parents as they aren't quite as up to date . Is there an alternative way of checking without a CRT?

The slower speeds (1/30 to 1/125) can be adjusted using a turntable using this method, but having a turntable around is also somewhat unusual nowadays. The really slow speeds (1/30 and slower) can be tested using a digital camera that can record video as per this thread (but it's unreliable for 1/30, especially if you don't know the exact frame rate of your camera).

The main point of the TV and the turntable is to provide fast-moving objects with a clearly defined speed. As long as you have something like that at home and know the numeric values, you can improvise similar testing methods yourself, but it takes some being comfortable with numbers.

Alternatively, you might build a shutter speed tester yourself. There's a lot of articles on the Web that describe how to build one - ranging from the simple to the intermediate and the elaborate. We've also had a couple of threads here at RFF, including a fairly detailed one.

Philipp

[Denis M.]

Originally Posted by fidget

Given that it's all clean and lubed, the part of the release mechanism which traps the second curtain isn't doing its thing. This is usually because the shaft which carries the crescent shaped catch is sticking (not cleaned or lubed properly). The shaft works on a very fine spring in two dimensions so is easily upset.

This question would probably be better posted in the FSU section as a new thread. More members will chip in with help.

This has been covered recently and is in a thread with some good detail. I will try to search it out.

I sprayed a cleaning solution on the bottom protruding rod and that seemed that have fixed the issue. It wasn't popping out all the way.

[payasam]

My FED-2's shutter is running fast, fidget, leading to under-exposure. I plan to rotate both nuts a half turn at a time. Do I rotate them clock-wise?

[Frontman]

The first thing you to is remove the lock screw from the nut. You have to be careful when making shutter speed adjustments, if you loosen the lock nut without using a screw driver to hold the spindle screw in place, it may turn fully out, and you'll completely lose shutter tension.

First, set the screwdriver in the spindle screw, and then turn the lock nut slightly counter-clockwise (if I remember right). Turn the spindle screw in the same direction to decrease tension, then, using the screwdriver to keep the spindle screw in place, tighten the lock nut and replace the lock screw.

You should try to adjust only the leading curtain, and just enough to bring it down to speed. If you get any capping, then reduce the tension to the following curtain as well.

[payasam]

Thank you, Frontman. I first turned the nuts clockwise a half turn each. That did not seem enough, so I turned them another full turn each. That seemed to be too much, so I went back a half turn each. The speeds seem better now, when seen against my monitor's screen, but I shan't know if they are right until I do tests on film.

[payasam]

Not good enough -- still getting underexposure. So I exposed several frames of the last roll with aperture set to meter recommendation for 1/100 sec. but with shutter at 1/50 sec. Perfect. I shall stick with this and not tinker more.

Something I do not understand. I did a series of exposures of a blank wall, starting at 1/500 and f/2 and going down to 1/50 and f/5.6. I did not get the same negative density: the fastest speeds were underexposed. This means that the speeds are not linear. Why this should happen with a shutter whose curtains should move at a constant speed, with only slit width varying, is beyond me.

[fidget]

I didn't notice these new posts for a few weeks!

It's sometimes seen when testing shutter performance that the gap can be irregular, having a slightly different gap over a few actuations at the same speed. I had put this down to a slightly poor setup on the release mechanism, but never really chased "why".

The actual shutter speeds are notoriously approximate, but I too would expect that their progression would be fairly linear, most certainly between two adjacent speeds.

A few on this forum have used electronic shutter testers. It would be interesting to learn how they found the speed progression.

Dave

[randomm]

Thank you for this precious info! I managed to tighten my Zorki 4K's second curtain, as it was really sticking with slow speeds (actually sometimes even with 1/30s which I now understand not being a slow speed).

Unfortunately I don't have a CRT monitor or TV at home so will have to check synchronisation at work later, however, I have encountered another problem: after tightening the second curtain axle by two full turns everything else seems to work fine, except now 1/30s speed occasionally acts like B ... anyone got any idea what's going on? Do I have to pull it completely apart for lubrication (not looking forward to that!)?

[wolves3012]

Originally Posted by randomm

Thank you for this precious info! I managed to tighten my Zorki 4K's second curtain, as it was really sticking with slow speeds (actually sometimes even with 1/30s which I now understand not being a slow speed).

Unfortunately I don't have a CRT monitor or TV at home so will have to check synchronisation at work later, however, I have encountered another problem: after tightening the second curtain axle by two full turns everything else seems to work fine, except now 1/30s speed occasionally acts like B ... anyone got any idea what's going on? Do I have to pull it completely apart for lubrication (not looking forward to that!)?

To answer your post in two parts:
First, two turns is a lot to have to add to make the second curtain close, almost certainly it suggests a proper CLA is needed. The "fix" is likely to be temporary I'm afraid. A second common cause for some speeds hanging is the spring that tensions that catch, it can put too much pressure on. This is more common at higher speeds though.

Second, why 1/30th acts like B. The second curtain is released by a catch, the crescent-shaped arm partially around the shutter speed selector. That catch is released by one of two things, either the first curtain reaching the appropriate position or by the shutter button being released. If it fails to get released by the proper mechanism (in this case the end of the first curtain's travel) then that adds more weight to the need of a proper CLA.

If you fancy braving it yourself, I wrote a thread specifically on the Zorki 4/4k which is stickied on this sub-forum,

[wolves3012]

Originally Posted by fidget

It's sometimes seen when testing shutter performance that the gap can be irregular, having a slightly different gap over a few actuations at the same speed. I had put this down to a slightly poor setup on the release mechanism, but never really chased "why".

The actual shutter speeds are notoriously approximate, but I too would expect that their progression would be fairly linear, most certainly between two adjacent speeds.

Fidget,

I can shed some light on possible explanations. First, as I'm sure you know, the curtains are not in any way linked and their speeds are not guaranteed to be the same. Second, on some models there is no positive latch for the cocking mechanism, therefore it's possible to cock it slightly short of 100% of the way, leaving a slightly variable exposure. Thirdly, on models with slow speeds I find that 1/15th is often inconsistent, this being due to how critical it is for the slow-speed mechanism to be wound to a small and *exact* extent, which the design doesn't really lend itself to. When using 1/15, I tend to set 1/8 then back off to 1/15. If re-cocking at 1/15 I'll wind it absolutely and very firmly to the stop.

[randomm]

Originally Posted by wolves3012

To answer your post in two parts:
First, two turns is a lot to have to add to make the second curtain close, almost certainly it suggests a proper CLA is needed. The "fix" is likely to be temporary I'm afraid. A second common cause for some speeds hanging is the spring that tensions that catch, it can put too much pressure on. This is more common at higher speeds though.

Second, why 1/30th acts like B. The second curtain is released by a catch, the crescent-shaped arm partially around the shutter speed selector. That catch is released by one of two things, either the first curtain reaching the appropriate position or by the shutter button being released. If it fails to get released by the proper mechanism (in this case the end of the first curtain's travel) then that adds more weight to the need of a proper CLA.

If you fancy braving it yourself, I wrote a thread specifically on the Zorki 4/4k which is stickied on this sub-forum,

Thank you very much for the info. Looks like I'm going to have to try to find a clear slot of few hours to have a proper look inside the camera. Don't get me wrong, I love tinkering with cameras - just have a pretty demanding 6 month old boy in my hands so finding time to tinker is a challenge!

[davip]

Hi!

I'm looking for an answer to my Fed 5b .

I have this video:

http://www.youtube.com/watch?v=8U4doaR5JGo

What happens is that in B mode, the curtain doesn't stay.

I have tried to adjust the speed of the curtains, but doesn't work.

All other speeds i think they are working good.

Only B mode and 30 i think they are wrong.

Hope that you have an idea!

David

[wolves3012]

Originally Posted by davip

Hi!

I'm looking for an answer to my Fed 5b .

I have this video:

http://www.youtube.com/watch?v=8U4doaR5JGo

What happens is that in B mode, the curtain doesn't stay.

I have tried to adjust the speed of the curtains, but doesn't work.

All other speeds i think they are working good.

Only B mode and 30 i think they are wrong.

Hope that you have an idea!

David

Try this thread, I think you may well have the same problem:
http://www.rangefinderforum.com/foru...ad.php?t=91895

[fidget]

Originally Posted by wolves3012

Fidget,

I can shed some light on possible explanations. First, as I'm sure you know, the curtains are not in any way linked and their speeds are not guaranteed to be the same. ...

Thanks for your reply to this old comment, and for fielding Q&A here.

As you might see in the original "how-to", I do claim that the curtains are "loosely coupled". So you could say that, no, I didn't know that they are not linked in any way.



My "how-to" did claim that the curtains tend to become synchronised when the curtain tensions are close enough, as (I believe) that the overlapping parts of the curtains and tapes, together with a shared/concentric shaft creates a loose coupling between them.
I have found that once set up, either curtain may be wound or released by as much a quarter turn to quite probably a half turn or more before this sync is lost, although the adjustment of any curtain may have an effect on the overall acceleration of the gap. But then, perhaps I have not found a way to measure shutter speed and fade accurately enough to see a difference. I assume that you are able to see this difference.

This thread is largely redundant at the moment, even if it is only due to the increasing rarity of CRT TVs. Perhaps someone could rethink a way to set up the curtains to a better accuracy.

[wolves3012]

Originally Posted by fidget

Thanks for your reply to this old comment, and for fielding Q&A here.

As you might see in the original "how-to", I do claim that the curtains are "loosely coupled". So you could say that, no, I didn't know that they are not linked in any way.



My "how-to" did claim that the curtains tend to become synchronised when the curtain tensions are close enough, as (I believe) that the overlapping parts of the curtains and tapes, together with a shared/concentric shaft creates a loose coupling between them.
I have found that once set up, either curtain may be wound or released by as much a quarter turn to quite probably a half turn or more before this sync is lost, although the adjustment of any curtain may have an effect on the overall acceleration of the gap. But then, perhaps I have not found a way to measure shutter speed and fade accurately enough to see a difference. I assume that you are able to see this difference.

This thread is largely redundant at the moment, even if it is only due to the increasing rarity of CRT TVs. Perhaps someone could rethink a way to set up the curtains to a better accuracy.

Fidget,

You're right that they are loosely coupled by sharing a shaft etc but I suspect that this is minimal, especially if (as I do) you lubricate that contact. I am theorising here, more than stating fact but I suspect the main reason they run at the same speed is the masses, drag and driving forces are sufficiently similar when they are cleaned and lubricated properly.

I don't have a suitable speed-tester, I still rely on a CRT monitor so I don't have access to accurate measuring means. One method I have tried, however, is to use a pair of laser-pointers aimed one each side of the frame. I use one red and one green and they are noticeably different in brightness. If that difference is apparent when firing the shutter, I reverse their positions and repeat. Assuming the difference remains, I assume the exposure must be reasonably even. Aiming one each side of the frame will also show capping and bounce. Not a quantitative test but it gives a general idea. One day I may take the trouble to build a speed-tester with a pair of sensors.

[john neal]

Fidget,

I would second Wolves view - there will be a very slight fluid link between the shaft and drum if it is correctly lubricated (probably due to sticktion IIRC), but that is minute in comparison to the kinetic energy associated with mass and speed.

I'm in the process of building a dual laser shutter timing device for LTM type cameras, and may be able to provide more info on this once I have got it working and debugged. If successful, I will be able to measure not only the exposure time, but also approximate (fairly accurately) the speed of the curtains as they cross the gate.

The intention is to allow for adjusting individual curtain tension to achieve best exposure across the frame.

More soon I hope

[fidget]

Thanks both.
What I can't reason away, is that "if" there is no tendency for the curtain mechanics to couple, and as you suggest, they operate totally independently, you will be very lucky indeed to get a speed match which is good enough to give an even exposure at the fastest speed. Any variation in the performance of either spring or associated mechanics will give rise to uneven exposure.
Whilst playing with several cameras, I see (or have seen, I don't do so much on these now) that a quarter turn on one curtain gave no change in the gap, but could be seen to run the pair faster across the gate. Given that they were totally independent, I would have thought that I should see a significant variation in the curtain gap as it opened or closed. On all the cameras that I can remember, adjusting by less than a quarter turn is not really an option as the lock nut has only four lock screw positions on it (if you choose to use them of course). Can tension be matched exactly in quarter turn steps?

I guess that we must "agree to disagree" on this one.

Incidentally, the "How-to" on curtain tension is pretty well based on this feature as it relies on setting up the curtains to run in sync then to adjust for travel rate. The loss of this fairly fundamental
feature (or observation/assumption) rubbishes this piece of work, wouldn't you think?

[wolves3012]

Fidget,

I'm not sure that we need to "agree to disagree" since I'm not claiming to be right or to know more. I'm merely pointing out that the two shutter curtains have no direct mechanical connection. They share a thin, lubricated (or should be) shaft and a short section of concentric bearing, so the fluid-drag has to be quite small. they also have ribbons that run over rollers on a similar connection (one pair of rollers on the other curtain's shaft). All of this will *tend* to make them "lock" if the difference in speed is minimal but I'm not convinced it's a major factor.

In addition, the curtains do have to run completely independently on the slowest speeds (1/20-1/30th and the clockwork-delayed speeds) and on B, so that would affect them badly if there were a significant connection. In addition, both curtains must accelerate and decelerate at the same rate if the gap is to be constant at high speeds and that part is definitely done whilst one or other is stationary. I suspect that the truth is that they actually don't run perfectly at all, the gap does vary a bit and our film latitude takes care of the bulk of this error.

Like you, I've experimented with tensions and found that large differences are required before a real problem occurs. I have actually tried to make a shutter cap when it was cleaned and lubricated properly; all I could really get was uneven exposure by grossly mis-tensioning one or other roller. Only by making the first curtain virtually slack could I get it to cap, since the second curtain pushed the first across (100% capping).

[batterytypehah!]

Originally Posted by fidget

This thread is largely redundant at the moment, even if it is only due to the increasing rarity of CRT TVs. Perhaps someone could rethink a way to set up the curtains to a better accuracy.

Not at all, and please do keep it up, guys. It's a great resource.

CRT TVs are going to be with us for a long, long time yet. Not in our living rooms, sure, but anyone who likes to tinker with a cloth shutter in the first place can surely keep one around in the basement somewhere for the purpose. Or find one for free, or nearly so, when needed.

[fidget]

Originally Posted by wolves3012

Fidget,

In addition, the curtains do have to run completely independently on the slowest speeds (1/20-1/30th and the clockwork-delayed speeds) and on B, so that would affect them badly if there were a significant connection. In addition, both curtains must accelerate and decelerate at the same rate if the gap is to be constant at high speeds and that part is definitely done whilst one or other is stationary. I suspect that the truth is that they actually don't run perfectly at all, the gap does vary a bit and our film latitude takes care of the bulk of this error.

Like you, I've experimented with tensions and found that large differences are required before a real problem occurs. I have actually tried to make a shutter cap when it was cleaned and lubricated properly; all I could really get was uneven exposure by grossly mis-tensioning one or other roller. Only by making the first curtain virtually slack could I get it to cap, since the second curtain pushed the first across (100% capping).

I hadn't intended to continue with this apparently trivial point, but your post here adds weight to my belief that the curtains do run "partially locked" (and in a small way, I am defending this sticky which is based on the loose coupling between curtains).

First of all, as you too have seen, very large changes in tension may be needed to get them to cap (on a clean cam, not on one which needs a CLA). If no loose coupling were involved you might expect a continuous degradation in the fade or gap as tension was changed.

Also, you point out, things are different on the slow speeds and B.
Quite so!

How many cams have you seen that appear to run OK on all speeds but 1/25 or B? It is easy to reduce tension to the point where the second curtain is unable to make the trip across the gate on 1/30th or B (where it has to make the journey alone) and yet still apparently work fine for the faster speeds. Is this not because at the faster speeds the second is "helped" by the first, or if you wish, there is a loose coupling between them that works for the shutters at faster speeds, and can work so much against it on B that the second curtain stalls.

Perhaps a weak coupling, but far from inconsequential.

[fidget]

Oh dear! It's starting to come over as a bit obsessive isn't it.

My apologies for this.

[wolves3012]

Fidget,

I'd hardly call it obsessive, I'd call it healthy discussion! Additionally, I'd just like to say I don't really think we're disagreeing nor do I want to appear confrontational or to claim some higher knowledge. All I'm pointing out is that there's no direct, mechanical coupling locking the two curtains in a solid fashion. I'm really not in a position to say that the small coupling that does exist is irrelevant but neither am I convinced that it's "the" factor, that's all. I think, perhaps, that we see the significance differently and who can say without greater knowledge of the design? Perhaps the truth lies in between?