Zorki 1 uneven exposure - worn out springs, dry mechanism, or something else?

[jim126]

Hello everyone. I am in the process of repairing my Zorki 1, and have come across a strange problem when calibrating the speeds.
I am using two photodiodes on either side of the film gate hooked up to an oscilloscope to measure the speeds of the shutter (I know I should have one in the center as well but I cheaped out a little there). I have two laser pointers pointed at them so when the shutter fires they output a signal for however long they are exposed for. Standard stuff.
The problem is, the left side of the shutter seems to be up to twice as fast as the right; the distance between the two curtains decreases as they travel.
I have tried increasing the tension of the first curtain a lot, and decreasing the tension of the second a lot - but to no avail. Looking at the negatives I made before I started tinkering with the camera, they seem to be evenly exposed (although I would have to print them - preferably with a high contrast - to know for sure).
I'm worried that I might have damaged the springs inside the shutter curtain rollers by tensioning them too much. Is that possible?
Also there doesn't seem to be any lubrication on the rollers, could this be the problem?
Thank you.

 

[Ko.Fe.]

Shutter drum springs must be washed out in camping fuel to remove old gunk.
Gun oil could be in use for new lubrication.
Also lubrication needs to be applied where is should be. It can't run dry properly.
If new curtains cut not precize or else not as it should, it will affect exposure.

But. I had perfectly Cla"d Zorky and after few months of regular use it gave uneven exposures.
I think metal is not good of those springs anymore.

 

[rfaspen]

I thought I read somewhere that the gap between curtains should decrease as they travel across the gate because of the accelerating speed of the first curtain. Wish I could remember where I saw that....

 

[Brambling]

With a particularly careful examination of any mechanism (not just the camera shutter), we can discover a bunch of inconsistencies with the theory, but only the final result can serve as a criterion for the correctness and fidelity of the operation of this mechanism.
Only taking into account all components of the process can help theory cope with practice.
The width of the curtain shutter gap at the beginning of the working path and at the end is different, the speed of movement of the curtains at the beginning of the working path and at the end is also different, which compensates for the change in the size of the gap.
Only the time of exposure to light of each individual point should be the same at the beginning and end of the shutter stroke.
You have the appropriate measuring device (I'm jealous here!) and the ability to change the speed of movement of both curtains by tightening the springs using the selection method.
Of course, it is necessary to remove all obstacles to the movement of the curtains, all burrs and unevenness of the tapes and rollers, rinse, clean and lightly lubricate the bushings in which the springs are located with frost-resistant grease; lubrication of the rollers is minimal.
I'm sure you will succeed.
You could hardly ruin the springs without using a large wrench)))

 

[Franko]

Not to rain on your parade but I've got two Fed 1s and a Zorki 1 and am amazed how consistently all three give uneven exposure. You'd think all three rolled off the line on the same day. Cleaning, lube and spring tension adjustment only caused the Fed shutters to sound more like Howitzers. I hope your luck is better.

 

[Brambling]

Excessive tension of the springs will not give the effect of correct operation.
There needs to be a balance.
The 1st and 2nd curtains in the first models are not connected to each other by a rigid mechanical connection.
Oscar's original idea, in my understanding, is that the spring will never give a uniform stroke - at the beginning of the working stroke it has a large potential energy and there is completely no kinetic energy, at the end of the working stroke the potential energy decreases, but a kinetic inertial component appears, the absolute speed of movement of both curtains increases, which means it is necessary to compensate for this by changing the gap width.
Therefore, balance is important and high tension of the curtains only gives a sound effect.)

 

[jim126]

With a particularly careful examination of any mechanism (not just the camera shutter), we can discover a bunch of inconsistencies with the theory, but only the final result can serve as a criterion for the correctness and fidelity of the operation of this mechanism.
Only taking into account all components of the process can help theory cope with practice.
The width of the curtain shutter gap at the beginning of the working path and at the end is different, the speed of movement of the curtains at the beginning of the working path and at the end is also different, which compensates for the change in the size of the gap.
Only the time of exposure to light of each individual point should be the same at the beginning and end of the shutter stroke.
You have the appropriate measuring device (I'm jealous here!) and the ability to change the speed of movement of both curtains by tightening the springs using the selection method.
Of course, it is necessary to remove all obstacles to the movement of the curtains, all burrs and unevenness of the tapes and rollers, rinse, clean and lightly lubricate the bushings in which the springs are located with frost-resistant grease; lubrication of the rollers is minimal.
I'm sure you will succeed.
You could hardly ruin the springs without using a large wrench)))

Thank you for the response. I agree that it is important to look at any other possible problems and the camera as a whole before focusing on something specific.
Maybe I'm misunderstanding you, but I don't see how the tool you use (screwdriver, wrench, etc.) could have any effect on the performance of the springs? I would think that tensioning them too much could wear them out/break them (isn't this is the same idea behind not leaving your shutter cocked for too long?). This is what I'm the most concerned about because like I said in my OP the photos I took before opening the camera seem pretty evenly exposed. The only think I changed was the curtain tension.

 

[Brambling]

Thank you for the response. I agree that it is important to look at any other possible problems and the camera as a whole before focusing on something specific.
Maybe I'm misunderstanding you, but I don't see how the tool you use (screwdriver, wrench, etc.) could have any effect on the performance of the springs? I would think that tensioning them too much could wear them out/break them (isn't this is the same idea behind not leaving your shutter cocked for too long?). This is what I'm the most concerned about because like I said in my OP the photos I took before opening the camera seem pretty evenly exposed. The only think I changed was the curtain tension.

For a big wrench - it was a joke)
I have never managed to break the springs due to too much tension)
But they jumped out of your hands and jumped all over the room - yes, that happened!)
Yes, there are different opinions regarding storage in a cocked or relaxed state.

 

[GMOG]

Here's what some of the old grease that I cleaned out of my Zorki 1 looked like:


The roller springs and shafts (up top in photo) were coated in a similar waxy, pasty residue:


Cleaning that sort of stuff out and replacing it with fresh lubes made my Zorki a reliable camera. I think it's the only way to make one work well. Splashing fresh oil on top of that old rancid paste is a temporary solution at best.

 

[felixm6]

Uneven exposure is a common problem with all FSU rangefinders. I have serviced down to the last screw about a dozen of them and none of them were within the tolerance of 1/2 stop between opening and closing at 1/100 and shorter. The good news is that you may not even notice it in most photos, unless you pay specific attention to it. I only found out about the serious imbalance when checking the speeds with an electronic shutter tester which I built recenty. The bad news: There is little you can do about it. The FSU Leica clones are far less responsive to curtain tensioning as the original or Japanese copies.

 

[Brambling]

The FSU Leica clones are far less responsive to curtain tensioning as the original or Japanese copies.

Why? Do you have an answer?

 

[felixm6]

No, don't really know the proper explanation. Perhaps the roller springs are of inferior quality and wear out. We are talking about 60+ years.

 

[alinCiortea]

Why? Do you have an answer

It's because the bloody Soviets "improved" the original design and physically linked the two curtains. The shutter speed selector has a pin that triggers the second curtain latch and at the same time locks onto the second curtain follower. Basically, the first curtain pushes along the second curtain, regardless of its spring tension. On one hand that means the gap between the curtains increases with a constant progression every time (that's the good part). On the other hand it means there's nothing you can do to change the gap (via adjusting the spring tension individually). This idea would actually work brilliantly if all parameters of the shutter would have been accurately calculated. But they weren't.
This is the Bane of my relationship with fixing these cameras.
And it's also the reason why soviet cameras barely react to changing the spring tension.

 

[Brambling]

It's because the bloody Soviets "improved" the original design and physically linked the two curtains. The shutter speed selector has a pin that triggers the second curtain latch and at the same time locks onto the second curtain follower. Basically, the first curtain pushes along the second curtain, regardless of its spring tension. On one hand that means the gap between the curtains increases with a constant progression every time (that's the good part). On the other hand it means there's nothing you can do to change the gap (via adjusting the spring tension individually). This idea would actually work brilliantly if all parameters of the shutter would have been accurately calculated. But they weren't.
This is the Bane of my relationship with fixing these cameras.
And it's also the reason why soviet cameras barely react to changing the spring tension.

All this is true - such a disease is present, however, nevertheless, not always, but sometimes))) I get uniform frames. How can you explain this?)