The Leica Ib is the only Leica camera with a Compur ‘between the lens shutter’, or Leaf shutter instead of the usual Focal plane shutter.
The Leica Ib was introduced in 1926, so one year after the Leica Ia. The camera had the normal Elmar 5cm 3.5 optics, but in this lens a Compur shutter was incorporated. The Leica 1B was made in two versions: the dial set type and the ring set type. 638 dial set types were manufactured until 1929. And 1072 ring set types from 1928 until 1941. Probably the last actual production runs stopped in 1932. And some 20 ring set types were assembled from bodies and lenses that were still in stock at the special request of customers.
Differences with the Leica 1a.
1 Shutter type: The Leica Ia had a focal plane shutter build in the camera Whereas the Ib had a Compur/leaf shutter build in the lens.
2 Shutter button: mushroom shutter button on the Ia had a different function on the Ib. There the button was used to unlock the film transport for advancing the film. On the Ib the shutter button was placed on the lens as well as a lever for tensioning the shutter.
3 Film transportation: On the Ia tensioning the shutter was done at the same time as film transport. On the Ib these were two different steps, which made it quite easy to make unintentional double exposures.
These all were disadvantages for the Leica Ib compared to the Leica Ia.
A big advantage however was the fact that the Leica Ib featured slow shutter times.
4 Slow shutter types: The Leica Ia had shutter times of Z (Time), 1/20, 1/30, 1/40, 1/60, 1/100, 1/200 and 1/500 sec.
The Ib had also slower times: Z, B, (D on the camera), 1, ½, 1/5, 1/10, 1/241/50, 1/100 and 1/300 sec.
In those days the film emulsion was still very slow, as were the lenses. Therefor there was a market for slower shutter times.
5 Wire release: Another difference compared to the Ia was that the Ib could handle the wire release that we still know today. The public had to wait until 1953 with the introduction of the Leica M3 for that same standard wire release.
6 Exposure counter: On the top plate of the Ia sits the time setting dial. On the Ib at about the same place the exposure counter is situated.
7 Dimensions: The dimensions of the body are the same for the Ia and the Ib. As a time setting and shutter tensioning lever are placed on the lens of the Dial set Ib the maximum diameter of the lens front is 54 mm opposed to only 36 mm on the Ia.
The total depth of body plus lens for the Ib is 71 mm, compared to 63 mm for the Ia.
The Ib weights 375 grams and is some 40 grams lighter than the Ia. This is caused by the more complicated mechanics for the film transportation and shutter tensioning.
8 Engravings: On both versions we don’t find the name Leica on the camera. On the Ia the name Ernst Leitz Wetzlar D.R.P. is engraved on the shutter dial housing. The Ib features a true Leitz Wetzlar logo between the finder and the rewind button.
9 Rewind release lever: The rewind release lever on the Ib works the other way around compared to the Ia.
10 Accessories: As the dimensions of the lens differ between the Ia and the Ib, there are different camera bags. Also the filter size differed, so different filters were available.
Ia with 3 roll film cassettes (Leona) and the Leica camera case Etrin: together this makes ‘Leica’
Ib with one roll film cassette (Lecus) and Camera case Etros: Lecom.
In 1929 the prices (in Swiss Francs) were:
Leica 1 a (Leona): 300 SFR
Leica 1b (Lecur): 250 SFR
So the Ib was 20% cheaper than the Ia.
Use in practice
The Leica Ib is a lot more difficult to use because the tensioning of the shutter and film transportation were two different actions. The shutter of the Ib fired very easily with double exposures as a result. One has to be very careful to tension the shutter at the same time as the transportation of the film.
F(riedrich) Deckel Munich manufactured the Compur shutter. And it has its own serial number on the side of the lens.
The body of the Leica Ib is very similar to the Mifilmca. This was a camera body that was designed to be attached to a Leitz microscope and used for photo microscopy. The film transportation was the same and also the Mifilmca was equipped with a Compur shutter. As this Mifilmca existed before the Leica Ib Leitz probably used the body design of the Mifilmca for the design of the Ib.
When Deckel changed the design of their Compur shutter to a more streamlined design (the Ring Compur) Leitz took over this design. More Ring type Ib cameras were made than the dial set types. This makes the value of the dial set type higher than the ring set type.
In Leica fact 17 I discussed the different versions of the Leica Ia. Many of these variations are also valid for the Ib.
Other Compur use by Leica.
Apart from the Ib and the Mifilmca cameras Leitz also used a Compur shutter on a very limited number (probably 58) of Summicron 50 mm lenses in 1956. As the shutter is in the lens, a special arm was made to make the connection of the shutter button on the top of the camera with the shutter lever on the lens. Rumour says that Leitz didn’t actually market this lens. Occasionally we see the lens mounted on a screw mount camera on eBay and other auctions.