Leica III shutter tension

Don_ih · Jan 19, 2024

I am currently fixing a Leica III that used to be a Leica I (1930). The camera had been taken apart who knows how many times, the shutter was not operating properly, screws were missing. I took it apart and cleaned everything nicely and have the shutter operating decently reliably. However, the exposure is not even across the image.

taken today with the sun at my back. The right side has less exposure than the left. I noticed a result like this in a test yesterday, so reduced the tension of the second curtain one notch. I'm not sure if that was the thing to do or if there should be something else. I have no idea what the tension on these curtains is, actually - anything could have been done to this camera in the past 94 years (including replacing the shutter mechanism, which I'm certain they did when they converted it to a III).

Advice would be appreciated. It's not a significant amount of uneven exposure (I could sweep it away with my hand while enlarging) but I'd like to have a better understanding of how the mechanism should be.

ic-racer · Jan 19, 2024

Without a proper shutter tester, achieving both even exposure and the correct exposure time will be extremely challenging.

Your second curtain is catching the first curtain.

There are some methods of shutter testing without a proper tester outlined in this pdf:

http://pentax-manuals.com/manuals/service/focal%20plane%20shutters.pdf

This is useful too:

Testing Shutter Speeds

National Camera Repair Guide

learncamerarepair.com

Don_ih · Jan 19, 2024

ic-racer said:
Your second curtain is catching the first curtain.

What do you mean? Before reassembly, I took a number of slow motion videos of the shutter operating, and the opening was always clear before the second shutter released. Or do you mean the second shutter is accelerating as it crosses the opening?

Will further reduction of the second curtain tension improve the situation? Or should the first curtain's tension be increased a bit? Is it possible that the first curtain is decelerating as it crosses and causing the variation of exposure?

ic-racer · Jan 19, 2024

Either the first curtain can slowed or the second curtain can be speeded up. Can you calculate your transit times with the slo-mo video?
Of the non-shutter-tester methods in the references above, there is no mention of slow motion video because that was unavailable to most people until only couple years ago. So, you will have to do the math yourself with frame-by-frame analysis.

Do you know the proper curtain travel times for that camera? I don't have it in any of my references, but it is a popular camera, someone should know.

If you check out the "Smarter Every Day" segment where they visit "Kamerastore" in Finland, you can see some transit time numbers from a Leica they are repairing. Though, it is unclear how far along they are with the repair. In this case curtain 1 is 16.4 msec and curtain 2 is 14.8 msec. The middle number is the shutter speed, 6.89 is near the lower limit for 1/125 per ISO.

Don_ih · Jan 19, 2024

ic-racer said:
the second curtain can be speeded up

The exposure improved when the second curtain was slowed (tension reduced).

I don't know the times for the curtain travel. The Leica III is not as popular as the IIIa or the IIIf. There seem to be some differences. It looks very dissimilar to the IIIf, for instance. And this is not the tension mechanism that is in the Leica I, which was much less sophisticated it seems.

ic-racer · Jan 19, 2024

This may help you also, from "The Leica IIIf, Larry Lyells, National Camera, Inc."

Attach the shutter speed dial and, if there is one, the flash synch cam, as these parts have rotational inertia that will affect shutter operation. With the shutter in the released position, that is, both laths at the right side of the image aperture, rotate the closing curtain spring adjustment 1 3/4 turns counterclockwise from its neutral position and the opening curtain spring 3 turns. At 1/30 second the shutter may operate with these settings, although more opening curtain tension may be required for reliable release of the closing curtain latch; increase tension 1/2 turn at a time until the closing curtain is released reliably. Now set the shutter at 1/500. Hold the camera with a light behind it, release the shutter, and check for an open slit across the full width of the image aperture. It’s likely that none or only part of the left side of the aperture will show light. Continue to increase opening spring tension until you see light across the entire width of the image aperture.
At this point some kind of shutter tester is required. You can use a TV screen if it’s an older set with a CRT; flat panel TVs won’t work. The TV should be tuned to a station to assure locking of the raster frame rate to the standard frequency. Or make a rotating drum tester from a coffee can, DC motor, and rheostat; see the last entry on the reference list.
Adjust the opening curtain tension in 1/4-turn increments for even exposure across the image aperture at 1/500. Then adjust the 1/500 and 1/1000 eccentric studs on the closing curtain latch for accuracy at these speeds. If you’re working on a pre-IIIc Leica, there are no adjusting studs. In this case adjust the opening curtain tension for even exposure across the image aperture at the camera’s highest shutter speed and accept the result.

Don_ih · Jan 19, 2024

Your quote - I've seen that before, those number of turns, but couldn't find it it - so that's handy. It won't be correct for this shutter mechanism, though - it doesn't work the same way. Quite possibly a good starting point - that last sentence is probably the one to pay attention to.

Don_ih · Jan 19, 2024

Don_ih said:
the opening was always clear before the second shutter released.

I should note that those were slower speeds.

I just took slow motion video of the 1/500 and 1/200 speeds (the fastest speeds) and there is a widening slit as the first curtain races away from the second - fairly drastic in the highest speed. So, I had it backward - misread my own image - irritatingly. So the second curtain maybe should be bumped back up a notch and the first slowed a notch.

@ic-racer -- thanks for your information.

awty · Jan 19, 2024

Don_ih said:
The exposure improved when the second curtain was slowed (tension reduced).

I don't know the times for the curtain travel. The Leica III is not as popular as the IIIa or the IIIf. There seem to be some differences. It looks very dissimilar to the IIIf, for instance. And this is not the tension mechanism that is in the Leica I, which was much less sophisticated it seems.

What's the difference?
The locking mechanism is usually different, but the function and adjustment is similar with any barnac camera I have worked on.
Either tightening or loosening the spring.

Don_ih · Jan 20, 2024

awty said:
What's the difference?

Minor ones, far as I can tell, such as what ic-racer quoted above "If you’re working on a pre-IIIc Leica, there are no adjusting studs. In this case adjust the opening curtain tension for even exposure across the image aperture at the camera’s highest shutter speed and accept the result." It's less sophisticated in general than the shutter in a IIIc.

So, yes, tighten or loosen the springs.

Don_ih · Jan 20, 2024

Well, gotta love the slow motion abilities of my phone. I had to speed up the second curtain to where is was and turn down the first curtain 3 notches. I can see an even gap on the higher speeds and, at 1/20, the curtains seem to be moving at the same speed (same number of frames to travel across). And the gap at 1/200 is very similar to another III that is working properly.

awty · Jan 20, 2024

Don_ih said:
Well, gotta love the slow motion abilities of my phone. I had to speed up the second curtain to where is was and turn down the first curtain 3 notches. I can see an even gap on the higher speeds and, at 1/20, the curtains seem to be moving at the same speed (same number of frames to travel across). And the gap at 1/200 is very similar to another III that is working properly.

Be good for another 90 years.

Don_ih · Jan 20, 2024

awty said:
Be good for another 90 years.

Yeah - if only the slow speeds worked....

Don_ih · Jan 20, 2024

The camera, by the way:

The skin (which had been painted glossy black at some point) was broken and broke off more when I removed the chewed-up screws, so I replaced it with leather. I made a paper template and cut the leather from a piece that used to be part of a sofa. I bought actually really good very thin double sided tape at a hardware store (who knew?). The Elmar is from who-knows-when -- it has no serial number. It looks like it was chewed up by something or other. It suits the camera.

(That making the skin went well is a bit irritating since I just ordered a skin online for another Leica III...)

Ballinderry-Michael · Jan 20, 2024

Don_ih said:
The camera, by the way:

View attachment 360577

-- it has no serial number.

Don, check the black ring at the edge of the front glass: there's often a serial number there, very small and hard to make out.

Don_ih · Jan 20, 2024

Ballinderry-Michael said:
Don, check the black ring at the edge of the front glass: there's often a serial number there, very small and hard to make out.

I have checked there. I own other ones with the serial number there. This one has no serial number anywhere.

Ballinderry-Michael · Jan 20, 2024

Don_ih said:
I have checked there. I own other ones with the serial number there. This one has no serial number anywhere.

Sorry for teaching you to suck eggs. Maybe the original aperture setting knob is away and the ring with it? Or maybe it's an extremely early version with a different setting arrangement.

Don_ih · Jan 20, 2024

Ballinderry-Michael said:
Sorry for teaching you to suck eggs. Maybe the original aperture setting knob is away and the ring with it? Or maybe it's an extremely early version with a different setting arrangement.

It's a normal f3.5-f18 Elmar 50. There are plenty of them with no serial numbers.

kl122002 · Jan 20, 2024

Perhaps the serial numbers have been worn out ? I have seen an elmar happened the same.

awty · Jan 20, 2024

The lens was probably used by a pre war spy and didn't want any markings to indicate which country it was purchased in. May have been transported in someone's rectum, so I'd give a good clean before using.

Don_ih · Jan 21, 2024

Interesting....

Uh, no. There were Elmars with no serial numbers. Some at least seem to be from converting the non-removable lenses from early Leicas when the cameras were converted to the O mounting flange.

Leica III shutter tension

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