Contax I ribbons

[Sarcophilus Harrisii]

Actually thinner ribbon would give a smaller diameter, more mechanical advantage and more acceleration as it rolled up but a lower top speed than thick ribbon would.

This would produce the exact effect that is being seen, where the low speeds that are governed would not be affected as much as the high speeds. If the Zeiss designers took this into account then the top speeds may not even be attainable with thin ribbon even with a perfectly and completely cleaned and lubed camera.

If the camera still has bearings with dirt and old lube in them on top of thinner ribbon than it is designed for then that would make the effect more pronounced because again the low speeds will be less affected but the high-speeds will be harder to reach because the frictional losses in a machine increase exponentially with speed.

Because the low speed is governed, the Contax that has the best chance to work at 1/500 and above will be one that has been completely taken apart, all clearances checked, all parts cleaned spotlessly, all lubricant replaced correctly and has the original diameter of the roll of ribbon when it is wound up at the end of the shutter travel.

That's a good point re: acceleration v top speed thanks for mentioning that and it does make sense.

I've taken a number of pics with the higher speeds of the IIs I have used Aki Asahi ribbons in but with few exceptions they're all on black and white negative which is more forgiving of additional exposure. But here are three photos made on colour transparency, which, on the other hand, doesn't give you a lot of latitude for a slower than optimal shutter.

1/1250 @ f/4 Carl Zeiss Jena coated 50mm Sonnar f/1.5 (this is the first shot of the roll, and an incomplete frame)

1/500 @ f/5.6 Carl Zeiss Jena 50mm as above

1/500 @ f/5.6 Carl Zeiss 50mm Sonnar f/1.5 (Oberkochen)

Overall those exposures don't look too bad to me and Provia is not going to give you a lot of room to hide if the shutter's dragging. Granted, the first image of the old truck (a WW2-era Ford Canada 4x4 vehicle as I understand it) shows the light green (faded) paint looking quite bright, but, it was late afternoon winter sun with the sun shining nearly straight at it, so, it's properly going to look quite bright as it is completely front lit. Incident readings were taken with my trusty Minolta Auto Meter III used to expose many rolls of transparency satisfactorily over of a number of years. I should stress these images were not made with the subject of the thread, the original Contax, but with a 36-37 Contax II (C serial prefix I believe) but they're tendered to demonstrate that the Aki Asahi ribbon can nevertheless deliver decent results In a Contax mechanism, even at the faster shutter speeds, if it is correctly cleaned and adjusted.
Cheers,
Brett

 

[Gben]

That's a good point re: acceleration v top speed thanks for mentioning that and it does make sense.

If the camera works it works, but I would still be very interested in empirical measurements of shutter speeds because I have pushed a lot of film with slower shutter speeds than is officially called for and I have never had any disasters. There are a lot of variables with any roll of film such as how it was stored, how old it is and on and on.

Those actual shutter-speed measurements would be the next step for this thread and help figure out what works and what does not. If everything can be gotten into factory specification with the thin ribbons that would be great. If there is still a ways to go I can think of one or two work-arounds to make up for the thin ribbon, and I am sure others here could too.

 

[Highway 61]

Those actual shutter-speed measurements would be the next step for this thread and help figure out what works and what does not. If everything can be gotten into factory specification with the thin ribbons that would be great. If there is still a ways to go I can think of one or two work-arounds to make up for the thin ribbon, and I am sure others here could too.

The problem is that we have no idea of what the "factory specifications" were. Best case, they used a cathodic oscilloscope to test their shutters (and they might even use someting less sophisticated, or nothing at all). Of course, none of the electronic shutter speeds testers available today were known by Zeiss Ikon in the 1930s. So if the "factory spec." for 1/1250 was 1/950 at the very best, what would getting 1/850 (with a cleaned shutter and ribbons slightly thinner than the original by a fraction of a fraction of millimeter) mean ? Nothing real. Add to this that 95% of handheld photos are shot at speeds between 1/30 and 1/250, whatever the film is, and the knot is tied out.

Chances are, that Robert Capa's Contax II cameras hadn't super accurate shutters. But the photos are still there.

 

[sevo]

The problem is that we have no idea of what the "factory specifications" were. Best case, they used a cathodic oscilloscope to test their shutters (and they might even use someting less sophisticated, or nothing at all). Of course, none of the electronic shutter speeds testers available today were known by Zeiss Ikon in the 1930s.

Opto-mechanical shutter testers consist of a pair of spinning discs (with patterns respectively slots) or are zoetrope-like. These must have been around by 1900 or even before. I've seen a similar tester still in use in the mid 1980s in a Nikon service centre - they can't have been much inferior to electronic testers. We can probably assume that Zeiss were technically capable of testing Contax shutters to a higher accuracy than the shutters themselves...

 

[Highway 61]

We can probably assume that Zeiss were technically capable of testing Contax shutters to a higher accuracy than the shutters themselves...

Absolutely. And we cannot know what the "factory specs" were for the Contax shutter highest speeds. Obtaining a true 1/500 and a true 1/1000 (or 1/1250) with a vertically travelling focal plane shutter became casual in the late 1960s. Before that...

 

[Deklari]

Absolutely. And we cannot know what the "factory specs" were for the Contax shutter highest speeds. Obtaining a true 1/500 and a true 1/1000 (or 1/1250) with a vertically travelling focal plane shutter became casual in the late 1960s. Before that...

I did test 1/1000 on my Contax I (1935) after curtain adjustment.
from 10 test only two give me 1/500. It is rally good. But I can't get 1/1250 on Contax III (1937) it always show 1/1000 or 1/500.
But what is the "factory specs" no idea. It is possible what after spending so much time on Contax I, I finally got 1/1000, what never been the case for this camera. Also after close the camera and loaded a film, I will not warranty it will still shut at 1/1000.

and 100% agree, "that 95% of handheld photos are shot at speeds between 1/30 and 1/250, whatever the film is" (!) Best solution used f11 and forgot about 1/1000 🙂

 

[Mr_Flibble]

Got about 15 Frames in on a roll of film before the film transport started to sound weird. Sounded like the film was skipping the sprocket teeth.
Could've been a loading error or something. I've rewound the film and developed half of it (the unused half went into the IIa).

I still see a difference in exposure of the images shot between the 1/100th in the medium speed and the sports group. I'll post some results from the scans later today.

 

[Deklari]

Got about 15 Frames in on a roll of film before the film transport started to sound weird. Sounded like the film was skipping the sprocket teeth.
Could've been a loading error or something. I've rewound the film and developed half of it (the unused half went into the IIa).

I still see a difference in exposure of the images shot between the 1/100th in the medium speed and the sports group. I'll post some results from the scans later today.

Same happens to me for first time. I replace a film spool (I don't have original). I have used old plastic spool from Kiev. I have cut a little from the top of spool. No problem after film cassette and spool alignment. It could be a different issue of course.

 

[Deklari]

and this link, just for everybody who want a really fast repair 🙂
http://www.hermes.net.au/bayling/repair.html

 

[Mr_Flibble]

Thanks Deklari, I'll look into it.

Meanwhile

1/100th medium speed group

1/100th sports group

Film is Fomapan 100, shot at the same aperture on the CZJ 5cm f/2.8 Tessar.
Film was developed in HC-110, Solution B for 6 minutes by 20C
Scans were down-scaled from 4800dpi with an old HP Scanjet G4050, auto levels , but no other post-processing.

 

[Erik van Straten]

I've rewound the film and developed half of it

In my opinion it is better after exposing not to rewind the film. The "rewind mechanism" of the camera is very primitive. The film is easily damaged during rewinding. When the film is exposed I open the camera in the darkroom, take the spool with the film out and develop it right away.

Erik.

 

[Deklari]

In my opinion it is better after exposing not to rewind the film. The "rewind mechanism" of the camera is very primitive. The film is easily damaged during rewinding. When the film is exposed I open the camera in the darkroom, take the spool with the film out and develop it right away.

Erik.

Agree. I really like my Contax I, even more then my Leica (sorry for Leica user, I still not get it, why Leica so "iconic"). But unlikely I will use it as a main camera for shooting or at list without any backup camera.

 

[Erik van Straten]

I found this little card in a Contax I neverready case.

Seems that Zeiss themselves thought that 1/100 was the ideal speed.

Corresponds to my experience.

Erik.

 

[Deklari]

I found this little card in a Contax I neverready case.

Seems that Zeiss themselves thought that 1/100 was the ideal speed.

Corresponds to my experience.

Erik.

Interesting, thanks Erik. I don't know how everybody shutting with they own Contex I. I just sett to 1/100 and lower the group (without changing speed), if I need increase exposure. in my Contaxt 1/100 given me 1/50, 1/10, 1/5 in different group. I have only move to 1/500 1/100 (in sport group) if bright light outside.

 

[Mr_Flibble]

The film is easily damaged during rewinding. When the film is exposed I open the camera in the darkroom, take the spool with the film out and develop it right away.

Something to keep in mind.
I did not think the surfaces the film runs across were that much different from the Contax II (or Leica LTMs) in design. Might be they're more coarse (or there's some aluminium-oxide), causing the scratches.

My take-up spool is supposedly an original that came with the camera. And in my case of the failing transport I suspect the leader might have come loose from the spool.

Ah well, at least now I can have a go at replacing the half-mirror.

 

[Highway 61]

My take-up spool is supposedly an original that came with the camera. And in my case of the failing transport I suspect the leader might have come loose from the spool.

The 1930s' films were thicker than our modern ones. Folding the leader before sliding it into the original take-up spool slot is a technique to consider. 😉

Also, I'd recommend to chamfer and polish the edges of the cassettes tensioning springs in the film chamber. Those can scratch the film, particularly on the take-up spool side. The tensioning spring on the take-up spool side can even be removed with no problem. But you'll have either to put the screws back (after having shortened them a little so that they don't make bumps under the front cover leather piece) or to fill the screws holes with black paint. There is s risk of light leak there if the screws are missing and the front cover leather piece is quite thin and not 100% lightproof, particularly in bright light conditions.

 

[Deklari]

The 1930s' films were thicker than our modern ones. Folding the leader before sliding it into the original take-up spool slot is a technique to consider. 😉

Good point. Sometime we forgot what live is a little different back to that time 🙂

 

[Deklari]

Ahh,.. have trouble today. Contax stop shutting at 1/100 (in sport group)
Shutter frizz. After switching group a few times it start "working" as "self timer", shutter respond only after 3-5 second. 1/200 works fine, but I can't really test all other speed I have half film inside.

 

[Highway 61]

Ahh,.. have trouble today. Contax stop shutting at 1/100 (in sport group)
Shutter frizz. After switching group a few times it start "working" as "self timer", shutter respond only after 3-5 second. 1/200 works fine, but I can't really test all other speed I have half film inside.

Maybe bat weazer izz too cold in terrrrible land you live ? 😀

More seriously : bad news, and best wishes for fixing it without having to spend many hours at it once and again. You should remove the film even if it's not finished. You may then find some film debris trapped in the shutter mechanism, or something like that.

 

[Mr_Flibble]

Sounds like something is sticky. Could be due to cold temperatures as Highway 61 says.

If you've got a darkroom or a change bag you could just open the camera and cut the film. Put the exposed part in a canister or a film tank.

Anyway, I hope it's nothing too serious.