wolves3012
Mentor
Try this thread, I think you may well have the same problem:
http://www.rangefinderforum.com/forums/showthread.php?t=91895
fidget
Lemon magnet
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
Mentor
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
fallor ergo sum
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
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
Lemon magnet
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?
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?
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wolves3012
Mentor
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).
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!
Lord of the Dings
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
Lemon magnet
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
Lemon magnet
Oh dear! It's starting to come over as a bit obsessive isn't it.
My apologies for this.
It's starting to come over as a bit obsessive isn't it. My apologies for this.
wolves3012
Mentor
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?
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?
ErnestoJL
Well-known
Gentlemen:
Both of you mentioned that some small coupling exists between the rollers for first and second curtains, which I do suppose is minimal and mostly due to the small friction between axes and rollers (even if properly lubricated). I wonder what would happen inside one of those "K" (kugellager) marked Leicas, which were factory fitted with ball bearings to avoid freezing problems. In this cameras, if lubrication and cleaning are OK, that coupling is nil (if ball bearings are in good shape) as well as friction between axes and shutter crate. Am I right?
If friction is zero, then the spring tension adjustment would be easier than with regular cameras.
BTW, thanks for a nice technical discussion which isn´t in any way obsessive.
Cheers
Ernesto
Both of you mentioned that some small coupling exists between the rollers for first and second curtains, which I do suppose is minimal and mostly due to the small friction between axes and rollers (even if properly lubricated). I wonder what would happen inside one of those "K" (kugellager) marked Leicas, which were factory fitted with ball bearings to avoid freezing problems. In this cameras, if lubrication and cleaning are OK, that coupling is nil (if ball bearings are in good shape) as well as friction between axes and shutter crate. Am I right?
If friction is zero, then the spring tension adjustment would be easier than with regular cameras.
BTW, thanks for a nice technical discussion which isn´t in any way obsessive.
Cheers
Ernesto
john neal
fallor ergo sum
Ernesto,
The balls sit between the shaft and the body at the top, and the drum and body at the bottom - the shaft to drum bearing is the same as on other Barnack cameras.
There will be less overall friction in a K that is set up correctly, but there is still the minute amount of drum to shaft friction. I have no way of mesuring it, or even estimating what it would be. My guess is that it's so small as to be insignificant.
The balls sit between the shaft and the body at the top, and the drum and body at the bottom - the shaft to drum bearing is the same as on other Barnack cameras.
There will be less overall friction in a K that is set up correctly, but there is still the minute amount of drum to shaft friction. I have no way of mesuring it, or even estimating what it would be. My guess is that it's so small as to be insignificant.
Fred2
Member
Hey fidget,
Thanks a lot for this threat!
Thanks a lot for this threat!
leonardo.mazzariol
Newbie
Fed 3 Curtain Video
Fed 3 Curtain Video
First of all I'd like to mention all these great recommendations!
Mainly fidget, thank you very much.
I'm writing to say that a friend of mine gave a FED 3 as a Wedding present. That was the first time I heard about it... after cleaning, repairing a hole in curtain I realized that pictures were unevenly exposed. So, I recorded the shutter using a high speed camera...
Will the tension adjustment correct this issue?
ps: I can't wait to go back to film cameras... ;-)
Links for videos below...
http://www.youtube.com/watch?v=kEYXtvta9FY
http://www.youtube.com/watch?v=gO_7lQKGwxw
http://www.youtube.com/watch?v=ZxZTNdamlSM
http://www.youtube.com/watch?v=TWE5B4zy7mU
Fed 3 Curtain Video
First of all I'd like to mention all these great recommendations!
Mainly fidget, thank you very much.
I'm writing to say that a friend of mine gave a FED 3 as a Wedding present. That was the first time I heard about it... after cleaning, repairing a hole in curtain I realized that pictures were unevenly exposed. So, I recorded the shutter using a high speed camera...
Will the tension adjustment correct this issue?
ps: I can't wait to go back to film cameras... ;-)
Links for videos below...
http://www.youtube.com/watch?v=kEYXtvta9FY
http://www.youtube.com/watch?v=gO_7lQKGwxw
http://www.youtube.com/watch?v=ZxZTNdamlSM
http://www.youtube.com/watch?v=TWE5B4zy7mU
wolves3012
Mentor
That's a really fascinating video, interesting way to see that the curtains don't move as they should. One thing that puzzles me, the second curtain should be detained momentarily (1/500th sec) after the first but the video suggests it is simply lagging behind and running slower. First thing, it's obvious that the speeds of the curtains are quite different, which is a tension issue - too much on 1st, not enough on second (either or both). After that the lack of pause in the second curtain might indicate a problem with the second curtain latch. I would suggest a video of 1/30th, where the pause should be very obvious because the first curtain should have completed its travel while the second is held.
Filzkoeter
stray animal
Something is wrong with the release for the second curtain. The video with the 1/15 speed shows it. Normally the second curtain should start to move after the first finished moving (at those slow speeds).
All Barnack Leica inspired shutters should work the same way: There is a disc for selecting shutter speeds. As you select your desired speed, you move a cam around which controlls when the second curtain is released (there is a lever... this lever catches the second curtain as you trip your shutter... the speed selector cam trips this lever and releases the second curtain).
Rick Oleson has written it down: http://rick_oleson.tripod.com/index-90.html
It could be possible that this "second curtain stopping lever" doesn't actually stop your second curtain. It would result that all your speeds are nearly the same... and uneven as both curtains are released at the same time but don't travel at the same speed (maybe because of wrong tensioning and/or dirt).
Does the B-setting work?
All Barnack Leica inspired shutters should work the same way: There is a disc for selecting shutter speeds. As you select your desired speed, you move a cam around which controlls when the second curtain is released (there is a lever... this lever catches the second curtain as you trip your shutter... the speed selector cam trips this lever and releases the second curtain).
Rick Oleson has written it down: http://rick_oleson.tripod.com/index-90.html
It could be possible that this "second curtain stopping lever" doesn't actually stop your second curtain. It would result that all your speeds are nearly the same... and uneven as both curtains are released at the same time but don't travel at the same speed (maybe because of wrong tensioning and/or dirt).
Does the B-setting work?
mburns
Established
Purchased after a CLA in Ukraine, my FED 2L had excessive tension on the curtains. Adjusting the tensions changed the sound of the camera. But there was a residual problem with hesitation in the second curtain at the 1/125 and lower speeds. Wearing in the shutter by exercising it eliminated the hesitation. But now the shutter times seem slower.
wolves3012
Mentor
All of this points to the lubricants being dried-up, in which case a proper CLA is the only cure. Sounds as though the one it got was a CLA without the CL bit! After a proper service , it should run sweetly for many years.
mburns
Established
Of course I can not disagree with that. There is a hesitation in the first curtain now. It's a FED 2D actually.
efinglada
Established
HiFidget,
I just got a Revue 3 with Industar 62 and have cleaned and aligned it following this therad. All speeds work Ok, but at 1/60 the 2nd curtain does not close, it sticks in the middle of the frame. At all other speeds the curtains open-close fine.
Can you please tell me where to start?
Thanks for the information
I just got a Revue 3 with Industar 62 and have cleaned and aligned it following this therad. All speeds work Ok, but at 1/60 the 2nd curtain does not close, it sticks in the middle of the frame. At all other speeds the curtains open-close fine.
Can you please tell me where to start?
Thanks for the information