Data sheet: Carl Zeiss Jena Sonnar 50 mm f/1.5 (Contax/Kiev)

Pekka Buttler, 02/2023

Carl Zeiss Jena Sonnar 50 mm f/1.5 (from 1940) with a Contax/Kiev mount


The table below summarizes the lens’ key specifications (measurements based on pictured lens):

Brand:Carl Zeiss JenaLens nameSonnar 1:1,5 f=5cm T
Focal length(s)150 mmAngle-of-view246 °
Maximum Aperturef/1.5In Production1932–≈1953 (all variants)
Lens mountsContax/Kiev, LTMSubfamily (if applicable)––
Length342,3 mmDiameter445,9 mm
Filter ring diameter40,5 mmWeight129 grams
Lens element count7Lens group count3
Aperture blades (S/R/C)513 SFocus throwN/A
Minimum focusing distance1,1 mMaximum magnification1:15,9
Has manual aperture ringYESHas Manual focus ringYES

Further notes:
• The f/1.5 Sonnar was originally introduced in 1932, and went through a number of minor redesigns during its lifetime.
• The Sonnar design was developed to minimise the number of air-glass interfaces, as these – before the advent of effective coatings – were a major source of veiling flare and had a negative impact on lens transmittance.
• Sonnar designs were initially used both for standard lenses and tele lenses. Subsequently, as coating technology improved – the Sonnar designs were replaced by double gauss designs in standard lenses.
• The pictured sample is from 1940 (based on SN), but already sports lens coatings. The pictured sample stems from the last redesign (1939)
• Pretty soon after the manufacture of this sample the accelerating war in Europe started curtailing lens manufacture, and after the war, manufacture of the f/1.5 Sonnar was not taken up again in Germany.

History of Carl Zeiss Jena

There are few names in camera optics more illustrious than that of Carl Zeiss. The company was founded in the German town of Jena in 1846 by Carl Zeiß (hence: ‘Carl Zeiss Jena‘). During 1846–1945 there are few major developments in lens optics that the company was not involved in. Names that are even today well-known in optics – such as Planar (1896), Tessar (1902), Sonnar (1929), and Biotar (1939) (as well as many names that only optics-buffs know) – were the product of Zeiss’ first century of technological innovation.

After the Second World War Germany was divided into a Soviet zone (subsequently: East Germany) and the west-allied zones (subsequently: West Germany). While the Zeiss works resided in Jena (optics and glasses) and Dresden (cameras), which were in the Soviet sector, a contingent of Zeiss managers decided to move west and ended up setiting up shop in the small town of Oberkochen in the American sector under the name of Opton Optische Werke Oberkochen GmbH. As the relations between the former allied deteriorated and the split into East and West Germany became all the more real, the Oberkochen works changed their name first to Zeiss-Opton and later to Carl Zeiss.

What ensued was a lengthy international trademark dispute with both Zeiss’ (Jena and Oberkochen) laying claim to the name ‘Carl Zeiss’. The resulting stalemate – emblematic of the Cold War in its entirety – resulted in that Carl Zeiss Opton was allowed to use the name Carl Zeiss in the West, but had to use the Opton brand in the East bloc, whereas Carl Zeiss Jena was the only real Carl Zeiss as far as the east bloc was concerned, but could – mostly – not use the Carl Zeiss -name for exports to the West6. The fact remains however, that – starting in 1946 from a shared base – Jena and Oberkochen developed as two independent companies for more than 40 years. After German reunification also Zeiss East and Zeiss West were united again, and have since again been at the undoubtable forefront of lens development.

This lens sample harkens to the time of the cold-war and the East/West split. During the entire Cold War period, VEB Carl Zeiss Jena was seen by the country’s leadership both as a paragon of the East German technology industry and a showcase of the socialist/communist system as well as a major source of exports (and hence, western currencies). Within the centrally directed economy’s hierarchy, Carl Zeiss Jena therefore had a more prestigious role than other East German optics manufacturers (prominently Meyer-Optik Görlitz and, later, Pentacon), meaning that Carl Zeiss Jena received privileged access to tools and materiel (including the first computer in East Germany) and that its products were always considered the premium alternative.

History of the Sonnar designs

The Sonnar designs were originally born out of necessity. Back before the invention of lens coating technology, each air-glass boundary a major, unwanted effect. Every air-glass boundary meant roughly 5% of the light that would hit such a boundary would be bounced back, instead of passing through the boundary. This not only meant that each air-glass boundary would decrease the amount of light that passed through the lens to the film plane, a goodly portion of that reflected light was liable to be bounced around within the lens, leading to veiling flare and loss of contrast. Hence, design a lens to minimise the number of lens groups was crucially important.

Until the invention of the Sonnar design, the only ways to produce large aperture lenses were based on the double-Gauss (a.k.a. Planar) and Ernostar designs, both of which were hampered by that the number of air-glass boundaries were relatively high (a minimum of 8). The Ernostar was the 1924 creation of the young (then only 23 years old) lens designer Ludwig Bertele for the company Ernemann. At the time of its launch it was – at f/2 – the fastest still camera lens in existence, and one year later Bertele bested his previous record with the f/1.8 Ernostar.

After Carl Zeiss acquired Ernemann in 1926, Ludwig Bertele continued pushing the boundaries and the Sonnar was a further development of the Ernostar. Not only did the Sonnar in 1932 manage to achieve an even larger maximum aperture (at f/1.5), it did so while simultaneously decreasing the number of lens groups to 3 (hence decreasing the number of air-glass boundaries to 6). It seemed like the perfect solution.

But it did not last long, Sonnar designs for standard lenses would never work on SLR cameras (that necessitated a significant back focal distance). Moreover, as lens coating technology advanced, one primary requirement for Sonnar-type lenses evaporated. After the war, Sonnar lenses remained popular on rangefinders (both as standard lenses and as short tele lenses), but after the advent of SLRs, Sonnar typed designs were reserved largely for large-aperture tele lenses.


During this era, development was continuous, and there are few outwardly easily distinguishable versions in existence. Hence, the serial number remains the best guide of the relative age of the lens.

Importantly, the earliest versions predate the widespread use of lens coatings (the red letter ‘T’ on the lens name ring indicates coatings are present).


n.B! The original Carl Zeiss Jena 5 cm f/1.5 Sonnar was mainly manufactured in the Contax/Kiev mount for Contax rangefinders. Besides that, a relatively short series of the lens using the Leica thread mount (LTM) were also produced. Furthermore, there are some examples of aftermarket modifications to other mounts, but these will be ignored.

Because the question of adapting Contax/Kiev standard lenses is a bit on the tricky side, I recommend you read the JAPB article on the Contax/Kiev mount, which also addresses the question in detail. Alternatively, you can also read the JAPB article on the LTM mount.


1 Focal length is (unless stated otherwise) given in absolute terms, and not in Full-frame equivalent. For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’.

2 Picture angle is given in degrees (based on manufacturers’ specs) and concerns the diagonal picture angle. Rule of thumb:
> 90 ° ==> Ultra-wide-angle
70–90 ° ==> Wide-angle
50–70 ° ==> Moderate wide-angle
40–50 ° ==> ‘Standard’ or ‘normal’ lens
20–40 ° ==> Short tele lens
10-20 ° ==> Tele lens
5-10 ° ==> Long tele lens
< 5 ° ==> Ultra-tele lens

3 Length is given from the mount flange to the front of lens at infinity.

4 Diameter excludes protrusions such as rabbit ears or stop-down levers.

5 S=straight; R=rounded; C=(almost)circular at all apertures.

6 Online one can find many lengthy and heated disputes stating that only Jena/Oberkochen is the true Carl Zeiss. While many of these discussions are riddled with misconceptions and a poor grasp of facts and timings, they largely also tend to be tainted by ideologies. Those discussions that focus on claims of one or the other Zeiss not really having rights to using designs developed at pre-war Zeiss are especially ludicrous because after the war practically the entire patent catalogue of pre-war German patents was given freely to everyone (the allied saw this as a form of reparations), hence also kickstarting the Japanese optics industry’s ascendancy (the Japanese optics companies were the most avid users of German optics patents).

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