Double-stroke M3. Why?

[pico]

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Any idea what the rationale was for the double-stroke M3? Was Leica considering a half frame at the time? I can make no sense of double-stroke. (But it's not the first time I was clueless.)

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[a.noctilux]

Leica M3 was the first lever-wind from Leitz. Before that, it was only button-wind. LTM's users will tell that it's not easy to wind-in-one-turn.

 

Leitz did not want to stress the film while winding too fast, so a breakage can occur.

Solution, split the winding time with "two-stroke".

 

After thousands of M3/M2 in everyday use with no film-destroy, Leitz came to "single-stroke" in production and "upgrade DS" when customers required.

 

Arnaud

[lars_bergquist]

The official reason was that fast winding in dry weather could lead to discharges of static electricity on the film. Like official reasons generally, this was a bit fishy. Not only had the Kine-Exakta used a single stroke lever since 1938, soon followed by various Retina cameras, Leitz themselves had offered rapid wind devices (SNCOO, Leicavit, even the MOOLY motor) for years, without disastrous results. In any case, most films at that time did already have antistatic front coatings over the emulsion.

 

I think it was general conservatism. When the M3 was launched at the 1954 Photokina, Walter Benser grumbled (in the LFI, actually!) that the wind-on lever irritated him. A Leica should have a big sexy winding knob. Period! I suspect that there were Leitz people who did not really believe in the wind lever; one or two M3 prototypes did actually use knob winding. So a double stroke lever would have been a kind of a compromise ...

 

The old man from the Age of the IIIf

[FiZZ]

I read that one of the reasons was tension. They were worried that the gears will increase the tension and the film will snap. The double stroke M3 uses two shorter strokes than a longer single stroke, therefore less tension.

 

Regarding the static electricity, that would only happen with glass pressure plates.

[ismon]

AND the single-stroke cameras could still employ two (or more, if you liked) strokes to wind the camera !

[lars_bergquist]

Regarding the static electricity, that would only happen with glass pressure plates.

 

The phenomenon was well known, and illustrated in some photographic handbooks, long before the M3 came along with its glass pressure plate. In any case, the phenomenon occurred on the emulsion side of the film. And early 35mm films were in fact quite sensitive to static build-up. That was why it had to be dealt with in emulsion making.

 

But it had in fact been dealt with already in 1954.

 

The old man

[scsambrook]

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The phenomenon was well known, and illustrated in some photographic handbooks, long before the M3 came along with its glass pressure plate. In any case, the phenomenon occurred on the emulsion side of the film. And early 35mm films were in fact quite sensitive to static build-up. That was why it had to be dealt with in emulsion making.

 

But it had in fact been dealt with already in 1954.

 

The old man

 

This is interesting to read - I'm no film technologist but I do recall a debate in the mid to late-50s in UK photo mags about 'static fogging' on film. The common perception was that the static discharge (is that the correct term?) took place between the film back and the pressure plate. 'Dimpled' pressure plates appeared in some cameras, allegedly to combat the phenomenon. The glass plate in the Leica was sometimes cited as an example of misplaced perfectionism. It was suggested that by using a glass pressure plate Leitz could (somehow) achieve greater film flatness in the gate than was possible with a metal one. 35mm film did indeed have a detectable curl which was visible from the front of the camera if you set the shutter on B . . . rather the reverse of the difficulties that sensors seem to pose.

 

Anyway, all that was rather reminiscent of the debates we see on here - only conducted at weekly or monthly intervals in printed journals. And in a universally ladylike or gentlemanly fashion.

 

I never saw any 'static' marks on my films, but I do remember seeing a distinct flash in the darkroom when pulling the taped end of 120 roll fim off its paper backing !

[lars_bergquist]

Yes, you could have it with roll film too, and you did not need a pressure plate -- not even a camera!

 

The old man

[Michael Hiles]

The same reasoning was behind the delay in changing the rewind crank to the version introduced on the M4.

 

Waste of effort, frankly. The M3/M2 system works fine with no meaningful reduction in speed.

[maxspbr]

The reason I really don't know. But I discovered myself using much more doubles (or more) strokes to advance the film in the M3 than just one. Looks to me quickly and easier.

 

Martin