Fed-2 shutter problem, uneven exposure

[Elektrojänis]

Hello,

This is my first message on this board and I'm not sure if this is the right area (this might also go to the repair/camera care).

I have been trying to tune up Fed-2 that my father has had for years. He has not used it though... It has been sitting on a booself at least for a decade or something.

Shutter was almost working... The first curtain seemed to work fine but the second was slow and tended to get stuck in the middle of its travel (worst on the slow speeds and bulb).

For a start I took it apart with the help of these instructions http://stephenc7.tripod.com/cameras/fed2.htm exept I have not replaced the shutter curtains yet. I might have to do that too, as i patched up quite many holes with fabric paint and it seems to have developed some more holes (or maybe i just missed them on the first time).

I tried to clean everything as well I could and lubricated the shutter with some sewing machine oil that feels very thin/light.

I also cleaned and lubricated the Industar-26m lens with these instructions: http://mattdentonphoto.com/cameras/industar_relubing/index.html

Everything seems to work nicely exept for one problem...

The problem is I can't get the shutter adjusted to give even exposures. I have read http://rangefinderforum.com/forums/showthread.php?t=30343 and some other istructions like the things on http://jay.fedka.com/ and some others.

I'm not using TV to measure the timings though... I'm using my own measurement setup with two photosensitive diodes, a soundcard (and a few resistors and 9 volt power supply) and some recording software. The photodiodes are set to "read" light from about 3-4 millimeters from the ends of the film opening.

I can get some of the speeds to give even exposures but not all. 250 and 100 are worst. 250 seems to give exposure time almost twice as long on the right side of the frame (looking from the behind the camera) that it gives on the left side. I can get 500 to be pretty even (a bit slow though if I dont want to overtighten but that seems to be typical from what I have read). I can get 50 to be decent (within 1/3 stop) and 25 almost as good as the 50.

On the 25 there is a difference though... left side will get more light.

Basically it seems that I should loosen the second cutain, but I do that, the 25 will get worse.

Some stuff I have read points that the curtains accelerate as they move (and thats quite logical when I think about it) and for this reason the "exposure slit" should get wider towards the end of the movement to get even amount of light to all parts of the frame (logical too). It seems to me that on the 250 and 100 the curtains tend to travel too much in sync and the acceleration causes the problem.

25 probably works the other way round because the second curtain is allready looser than the first and on 25 the curtains cannot "get stuck in sync" like that because the curtains dont move at the same time (second curtain starts moving when the first stops). I can actually get the 25 to be quite perfect but then the others will get worse (or at least not better).

I have not yet put any film through this, but I'm pretty confident my measurement rig is accurate enough that tho problems I have observed are real.

So has anyone else noticed this kind of behaviour when tuning their FSU-cameras? Can anything be done to it or is it just the nature of the beast?

Although it seems to me very thin/light the sewing machine oil could be a bit too heavy/sticky for the shutter, but could it really cause this kind of trouble? Or is there something else that could cause this?

-Petri

 

[wolves3012]

Petri,

Firstly, welcome to RFF!

With regard to the shutter speeds, remember that they will never be all exactly correct and perfectly even. A difference of half a stop will hardly be noticed except perhaps with transparency film. Try the TV test as well as using your speed tester, you may be surprised.

One area to look into is that a tiny amount of thin oil may be needed on the shaft of the curtain drum. That needs to rotate independently of the shaft, if it can't then the two curtains tend to drag oneanother along or brake each other due to them being on a common pivot.

From personal experience, a well cleaned and lubricated shutter can need as little as 3 turns on the first curtain roller and 2 on the second. The first curtain should always be a bit snappier then the second.

Good luck and let us know how you get on. Just don't expect perfection in an old, mechanical shutter!

 

[Elektrojänis]

Now that I think of it, the shaft of the curtain drum could be the problem. I tried to get some oil there, but that was the most difficult spot, and I'm not too sure I got the oil to the right place.

Actually, I think I'm going to replace the shutter curtains as I thought I might have to anyway. It's probably easier to clean and lubricate the curtain drum properly after removing the curtain from it.

Before this I thought that I could patch the curtains enough to take a few rolls pictures with it, but as almost always, it's probably better to do this properly at once.

I'm not really expecting this to be a precision instrument although I'm quite amazed how repeatable some exposure times I have measured have been. I probably could live just fine with half stop difference between the sides, but currently at 100 there seems to be a difference of full stop there.

I'll try the TV-method too for the measuring. I might even do a "sanity check" with my measurement setup by measuring my Nikon F2 that has been tuned by a camera repair shop a few years ago.

Thank you for the tips! I'll post my experiences when I get more work done on this.

 

[Elektrojänis]

I haven't made much progress as I haven't yet got the curtain fabric to replace the old curtains. One thing I did though... I tested my measuring setup by measuring the speeds of the Nikon F2. Most of the speeds are fairly accurately what they should be and are nicely very even from side to side. In other words: My measuring setup seems to work fine. I'll probably try the TV-method on the Nikon F2 too so I'll see what things should look like with that method.

The downside of the experiment: Almost all speeds of the Nikon F2 seem to be what they should be... Almost... The top speeds seem to be too slow. If I wouldn't have known it wouldn't have probably mattered at all (I rarely use those top speeds anyway), but I tend to be a bit too strict about these things... Well... Maybe the Fed-2 will teach me something about details vs. the big picture... 🙂

Edit: I Added the word nikon to few places so it is easier to distinguish between two cameras I'm writing about.

 

[nzeeman]

maybe some more speeding up of both curtains will give you more precise high speeds? i think it will not affect slow speeds...
also one question - are your exposures even now?

 

[Elektrojänis]

Oh... Sorry... I was not too clear on this: I just measured another camera with my measuring setup (Nikon F2) to see that my measurements are correct. I have not yet continued with the Fed-2 yet, as I'm waiting to get some shutter fabric to replace the curtains.

So it was just kind of status report...

 

[Grytpype]

Hello Petri,

Your problems are very similar to those I have been struggling with on a couple of Exaktas for much longer than I would care to admit. A different shutter, obviously, but I believe they work (or more often don't!) on similar principles. You seem to have a very good grasp of what is going on in the mechanism. I would tie it down to 2 basic issues: -

1. The inertia loading on the two curtains is different, which makes it impossible to adjust the tensions so that they start the frame at equal speeds and accelerate equally across it.

2. The curtains do not run completely independently, nor locked together, but there is some drag between them because parts of the mechanism (the drums on the FED) run on the same spindle. This means that the first curtain's overall speed varies at different shutter speeds depending on how far it travels across the frame before releasing the second curtain, and the second curtain's overall speed varies depending on how much of the frame it travels after the first curtain reaches the other side. This means that even if you can get the curtain tensions adjusted to give good results at one speed, it will be wrong at all the others, and accounts for the reversal of the error at 1/25 you have found. Obviously this problem compounds with the first to make things even more interesting!

Hopefully wolve3012's suggestion of oiling the drum spindle might help with the second issue (see his Zorki 4k CLA sticky http://rangefinderforum.com/forums/showthread.php?t=33914 - there is a pdf of the whole thing you can download). However I've got to say that oiling the equivalent position on the Exakta doesn't help!

I'm not an enthusiast for the monitor/TV shutter test. At best it is a rough guide for the medium speeds. At the high speeds it is pretty useless. Your photo-diode set up is a better prospect, but for accurate timings make sure your light source is as small and distant as you can manage and that the apertures over the diodes are also as small as you can make them (a narrow vertical slit). If you haven't done this it could be the reason the fast speeds on your Nikon appear slow. I use a home-made tester with 3 photo-transistors at start, middle, and end of the frame. At the faster speeds you can combine the outputs of the start and end transistors and get the results from all three on the 'stereo' recording on your sound card. Also, I've just made a tester with 2 photo-transistors at 2mm spacing so that I can measure the curtain speeds at any point in the frame. This is interesting, but hasn't enabled me to fix my Exaktas yet.

Let us know how you get on. It would be very encouraging to see you get the FED working properly, because after my Exakta experiences I'm too scared to make a start on my two Zorkis!

 

[Elektrojänis]

Your photo-diode set up is a better prospect, but for accurate timings make sure your light source is as small and distant as you can manage and that the apertures over the diodes are also as small as you can make them (a narrow vertical slit). If you haven't done this it could be the reason the fast speeds on your Nikon appear slow.

I have the photodiodes in a small black plastic box (electronics project box) that is small enough to fit nicely behind the shutter but big enough to cover the film opening (it can rest nicely on the "film tracks" or whatever they are called). The holes for the diodes are round but their diameter is only about 1 millimeter. The plastic is also 1-2 millimeters thick and I thought that might also help the accuracy as the diodes get light more just straight from the front and not from the sides.

The light source has been very close and big(just a regular energy saver bulb). I thought that the small holes etc. might help to counteract this. I'll look into this and try to improve my setup although the Fed-2 maximum speed of 1/500 might not need much better accuracy.

I use a home-made tester with 3 photo-transistors at start, middle, and end of the frame. At the faster speeds you can combine the outputs of the start and end transistors and get the results from all three on the 'stereo' recording on your sound card.

That's a very cool idea... Three with a price of two! 🙂

I have thought of measuring the center too, but that kind of thing didn't even cross my mind... I was thinking of using one more soundcard channel (Because of some other hobbies I have one that has 4 channels).

Let us know how you get on.

I will! Now I'm still waiting for the curtain fabric I ordered to arrive.

 

[martin_t]

Hello Petri,

I'm not an enthusiast for the monitor/TV shutter test. At best it is a rough guide for the medium speeds. At the high speeds it is pretty useless.

I'm curious, why would the TV test be useless at 1/500 or 1/1000?

 

[fidget]

I'm curious, why would the TV test be useless at 1/500 or 1/1000?

I was wondering this too.
I've found that 1/500th and 1/250th is pretty good for testing the shutters, but this will be due to the screen refresh rate that I have, YMMV.
The slower speeds of 1/60th and 1/30th are so slow as to be not practical speeds to test on, these giving such wide strips as to overlap, but again this will be a factor of my set-up.

It's perhaps interesting that, even with the screen test, it's easy to see that there is some significant variation in shutter releases. Setting up to the n'th degree may be of limited practical use.

Making a tester sounds like a great idea, I like gadgets. I guess that they could be used for any shutter, leaf shutters too?

Good luck with your project.

 

[Elektrojänis]

Making a tester sounds like a great idea, I like gadgets. I guess that they could be used for any shutter, leaf shutters too?

I can't see why the photodiode tester couldn't be used for any kind of shutter as it really measures the time how long the shutter let's light through.

Accuracy of the measurement is of course in the details of the setup as discussed above. In addition to hole sizes and light sources the accuracy of the soundcard and the rise/fall times of the photodiodes will affect the accuracy of the measurement. Fortunately, most photodiodes are quite fast and most computer souncards/soundchips should be accurate enough. (If the sampling frequency is more than 10% off it should be pretty easy to hear it when listening familiar music through it.)

My current setup is bit or a mess of wires and stuff and only has two photodiodes. I'm actually thinking of building a tester with 5 photodiodes in it. Diodes for top, bottom, left side, right side and center and then a mechanism to choose which ones I want to measure. This would probably cover most of different shutters (horisontal, vertical etc.) for 35mm cameras. I'm just not sure if it's really worth it, because I'm not sure if I'm going to repair any more cameras in the future.

 

[Grytpype]

Hello Folks,

Maybe I'm doing it wrong, but the reason I don't find that the monitor test is very useful at the higher speeds is that you get such a narrow stripe, and unless it just happens to occur at the the point in the frame you want to examine (usually the start) it doesn't tell you anything you need to know, and it won't show whether the exposure is varying across the frame. I must admit I haven't tried too hard!

I think that probably a 1mm hole over the diodes is enough to increase the readings above their true values at 1/500, particularly if your light-source is close. I started off doing the same thing, but realised that I was getting results at the higher speeds which were impossible, given the width of the slit between the curtains and their speed. I made a mask with narrow slits and moved the light-source further away, which gave far more sensible figures. My tester is actually very much like the one you're planning, Petri (they say great minds think alike!). I've written a rough description at http://www.ydo.abelgratis.co.uk/shutter_tester.html which might give you some ideas.

This sort of tester is OK for a diaphragm shutter at medium to low speeds but difficult to get an accurate result at higher speeds because here the speed at which the shutter-blades move becomes an issue, so that a graph of the light getting through would be a bell-shaped curve rather than a nice square pulse. I've been thinking about trying to devise a tester that would work by integrating the output from a photo-transistor - effectively measuring the area under the curve - and the other day I found some data for a chip that might do it, but I'm no electronics whizz so don't hold your breath! There is a design I've tried which works by charging a capacitor from the photo-transistor, but it seems too non-linear to work properly.

Best of luck with the curtains.

 

[Grytpype]

I've just re-read your description of adjusting the tensions by the monitor/TV method, fidget, which is the clearest explanation I have seen. Having tried a bit harder to get it to work on one of my problem cameras I have to admit that it does show valid results, even at the high speeds, but as you say in your notes it definitely can be "fiddly" and "tedious"!

 

[fidget]

I've just re-read your description of adjusting the tensions by the monitor/TV method, fidget, which is the clearest explanation I have seen. Having tried a bit harder to get it to work on one of my problem cameras I have to admit that it does show valid results, even at the high speeds, but as you say in your notes it definitely can be "fiddly" and "tedious"!

Yes, maybe that aspect was understated. It's very hard on the winding fingers too, particularly on knob winders.

 

[Elektrojänis]

Hello Folks,
My tester is actually very much like the one you're planning, Petri (they say great minds think alike!). I've written a rough description at http://www.ydo.abelgratis.co.uk/shutter_tester.html which might give you some ideas.

Whoa! That really looks a lot like what I have been thinking. 🙂

Your setup looks really clean, nice and well thought. You have documented it really good too. I wonder why I haven't found your page before even I have tried googling this kind of stuff quite a lot.

My current setup is not quite as clean: http://koti.welho.com/pjunno/temp/shutter_tester.JPG

The breadboard is only used for the resistors and for connecting jacks for the soundcard. There is also another unrelated project still on the breadboard.

Hmmm... One thing that might improve the results and make the light source setup less important could be if the "acceptance angle" of the photodiodes/phototransistors could be made narrower. Maybe that could be achieved by moving them deeper in the enclosure.

This sort of tester is OK for a diaphragm shutter at medium to low speeds but difficult to get an accurate result at higher speeds because here the speed at which the shutter-blades move becomes an issue, so that a graph of the light getting through would be a bell-shaped curve rather than a nice square pulse.

If the pulse ramps up the same speed as it does ramp down, that really should not bee too much of a problem. The measurement could be taken from the moment the signal starts to rise to the moment it starts to fall.

Also... Some part of the "sloping" of the pulse might come from the photosensitive devices too. Generally phototransistors should be fast enough but I read some datasheets today and it seems the swiching speed is also dependent on the current used. You might try using a bit more current. I would try changing the 56kohm resistors to 10kohms or even lower and maybe using a bit more voltage than 1,5V. It seems to be common in the datasheets to specify the turn on and turn of times with 5V, 5mA. That makes the resistor 100ohms.

This all might be familiar to you, but I thought that no harm will be done by mentioning what I've found out.

I've been thinking about trying to devise a tester that would work by integrating the output from a photo-transistor - effectively measuring the area under the curve - and the other day I found some data for a chip that might do it, but I'm no electronics whizz so don't hold your breath!

Sounds interesting. It could maybe be even used whithout a computer (simple voltage measurement of the output)?

I'm no electronics whizz either, but many times it's quite amazing what kind of stuff can be designed and built with just basic understanding of current, voltage etc. and just reading some datasheets and checkin out some web pages.

 

[Elektrojänis]

It's very hard on the winding fingers too, particularly on knob winders.

Almost any testing is hard on the winding fingers anyway.

Heh... When I started cleaning the Fed-2 I did a lot of testing for the mechanism with no winding knob at all... I just cocked the shutter from the sprocket wheel... At first it was ok, but after a while it started to really hurt my thumb.

I got to admit, that your description of the TV method is very clear and easy to understand. My biggest reasons for using the photodiode/phototransistor method is because I wanted a bit more precise method to determine the actual shutter speed (I dont trust my visual memry that much) and I only have one CRT screen and usually when I'm tinkering whith camera stuff it is in other use (my significant other is watching TV 🙂).

 

[Grytpype]

I'd certainly agree now that the monitor/TV test is a viable option, though I am always conscious that the wear I am putting on the camera while I am trying to adjust it is about 100 times what I could give it in 50 years of putting film through at the rate I take photos. I think the monitor test could multiply this by a factor of 10 or so! I'll use it as a quick test before putting a film in, though, just to check correct functioning.

You're probably right that moving the transistors/diodes back from the apertures would make a tester more accurate, Petri, though it might be more difficult to construct accurately. Interesting comment about the voltages/resistances. I went for 1.5v for convenience, and if the resistance is too small the output gets too tiny to see. I haven't seen any data for photo-transistors. I have assumed that their response time would be of the same order as ordinary transistors and anyway I'm fairly sure they are going to be so much faster than anything we are dealing with in a shutter that it is not worth worrying about, even if they are not being driven under their intended conditions.

It is a long while since I tried my tester on a diaphragm shutter, and I can't remember exactly what the waveform looks like, but your suggestion might work. The idea of making an integrating circuit tester is that it would give a direct comparison between the speeds. Output would be, as you guessed, direct to a digital volt-meter.

My pages are just in the free web-space ISPs give you when you sign up. They don't seem to come up in Google searches. I'm not sure why.

 

[Elektrojänis]

Sorry to bump up a really old thread, but I think I have finally got this thing to work somewhat decently. The real test will be putting some film through it. I've already loaded in the first roll (just some regular 400ASA Fujicolor for testing), but it will probably take some time to fill it.

My problem with the uneven exposures remained no matter what I did, untill I tried to loosen up the curtain tensions somewhat so that all speeds are a bit slow. They are still a bit more uneven than I'd like, but I think they are usable now.

This is what I got with my measurement setup (if my copy-paste from excel works):

nominal start   middle  end
500     298     336     322
250     146    201     198
100     63    74     84
50     39    37     39
25     21     17     14

Nominal is the speed set on the dial. Start is about 4mm from the right side of the film gate, middle is about in the center and end is 4mm from the left edge of the film gate.

If I tighten either or both of the curtains even half a turn, it will make the speed across the frame even more uneven.

I think the problematic part might be this: http://stephenc7.tripod.com/cameras/fed2/28_ShutterSpeedPin.jpg (image 28b on http://stephenc7.tripod.com/cameras/fed2.htm)

It and the shaft of the curtain drum seem to stick to each other a bit no matter what I did. I actually ended up using bit thicker oil than the sewing machine oil I used on the rest of the shutter and it seemed to work somewhat better (although not much). I even tried some grease but it did not help any more (surprisingly it did not make it much worse either).

Only thing I did not try is getting some real shutter oil. That might "cure" it, but I'm not convinced that it would make that big difference.

 

[Elektrojänis]

I finally got my test roll developed and did a "quick and dirty" scans of the negatives: http://koti.welho.com/pjunno/temp/fed_q_d_jpg/

Some of the pics show something like a light leak on the left side. For example img010.jpg and img018.jpg... Could this be that it is a light leak from between the curtains that happens when cocking the shutter?

Anyway... Other than that light leak thing, the camera seems to work fine (enough for what I intend to do with it). If it is a light leak I might take it apart again, and set the curtains to overlap a bit more when cocking the shutter (re-glue the second curtain or the first curtain tapes just a bit different spot on the drum). The other option is using a lens cap when cocking the shutter. 🙂

Thanks for everyone who helped!

 

[KGB-Spion]

Hello,

like the others, I had the same light leak on the left side in 2 of my cams! Don`t worry - its usual, when the 2.nd courtain sticks a little bit OR when You cock, then at the left side, there is a small leak until the curtains go together !

About the shutter speeds: Urggggh -- I really hate it when I get a new cam and the shutter speeds are different ! It takes about 3 or 4 hours for getting them in acceptabe standards!


BUT: does anybody know the tollerances ?