Data sheet: Carl Zeiss Jena Flektogon 50 mm f/4 (Pentacon 6)

Pekka Buttler, 04/2024

Specifications

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

Brand:	Carl Zeiss Jena	Lens name	MC Flektogon 4/50
Focal length(s)1	50 mm	Angle-of-view2	76,4 ° (on medium format)
Maximum Aperture	f/4	In Production	1960–≈1990 (all variants) ≈1966–1990 (this variant)
Lens mounts	Pentacon 6	Subfamily (if applicable)	––
Length3	73,7 mm	Diameter4	89,8 mm
Filter ring diameter	87 mm	Weight	630 grams
Lens element count	7	Lens group count	4
Aperture blades (S/R/C)5	8 S 6	Focus throw	300 °
Minimum focusing distance	0,5 m	Maximum magnification	1:8
Has manual aperture ring	YES	Has Manual focus ring	YES

Further notes:
• The 50 mm f/4 Flektogon was originally introduced in 1960, together with the 25 mm f/4 Flektogon for 35 mm film. Before the 50 mm f/4 Flektogon’s introduction, the widest lens for the Praktisix/Pentacon Six system was the 65 mm f/2.8 Flektogon.
• Early on, production was very limited due to the difficulties inherent in the lens’ manufacture. The 50 mm Flektogon was recomputed in 1966 to enable a more economical manufacturing process, and most surviving samples are of this later design.
• All copies of the 50 mm f/4 Flektogon are radioactive, but the earlier (pre-1966) design is significantly more radioactive.
• While not the widest rectilinear lens for the Pentacon Six system (that title goes to the MIR-26b 45mm f/3.5 [data sheet]), it is the widest Pentacon Six lens by Carl Zeiss Jena. It was also a relatively successful lens (in terms of production numbers).

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 West⁷. 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. 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.

After German reunification also Zeiss East and Zeiss West were united again, and have since again been at the undoubtable forefront of lens development. Even though it was manufactured after reunification, this lens sample harkens to the time of the cold-war and the East/West split.

History of the Flektogon designs

Carl Zeiss Jena was a central player in the development of a class of lenses today known as retro focus lenses (a.k.a. reversed tele focus) – a key approach to allowing the manufacture of wide-angle SLR lenses. While the jury is out on whether Angenieux (France) or Carl Zeiss Jena actually was the first company to bring the concept into production, it is evident that Carl Zeiss Jena was both genuinely innovative and prolific in this niche.

The ‘family name’ of Carl Zeiss Jena’s retro focus wide-angle lenses was ‘Flektogon’ (Carl Zeiss West called its corresponding family ‘Distagon’). The Flektogon family contained lenses with focal lengths of 20, 25 and 35 mm (for 135 film) and 50 and 65 mm (for 6×6 medium format).

Versions

During its 30 years of remaining in construction, there were two optically distinct versions of the 50 mm Flektogon. The first was manufactured in relatively low numbers during 1960–66. The second version was produced between 1966 and 1990 and reached roughly 75 000 produced samples – a respectable number for a medium format SLR lens.

The later version was produced in a wide range of contemporary Carl Zeiss Jena outward designs, from the early silver and faux leather, through the classic, black-and-silver ‘zebra’ looks to finally end up with the all-black design pictured above.

Adapting

The Pentacon 6 mount offers a wide range of alternatives for adapting.

To use this lens natively, you will need a Pentacon 6 mount film body. In practical terms this means either a Praktisix or Pentacon Six medium format film camera or a Kiev 60/6C medium format film camera. While neither of these families of bodies were manufactured in their millions, they remain readily available, and even serviceable.

Thanks to the generous image circle Pentacon 6 lenses offer, and thanks to the copious flange focal distance (74,1 mm) of the Pentacon 6 system, this lens can be adapted to every full frame (and smaller) SLR, dSLR and mirrorless camera assuming a suitable adapter can be found or manufactured. Moreover, Pentacon 6 lenses are so uncomplicated that a simple ‘dumb adapter’ will do the job perfectly.

Thanks to the generous image circle, Pentacon 6 lenses have also long been a strong candidate to be used on smaller formats (full frame and smaller) in conjunction with tilt/shift adapters. Alternatively, one can choose to daisy-chain adapters (e.g. Pentacon 6->Canon EF; Canon EF –> mirrorless) which not only broadens the range of available adapters, but also allows using speed boosters for those photographers that use smaller than full-frame sensors.

Finally, regarding larger than full frame, there are also options. Digital medium format is perfectly usable (assuming adapter availability) and many 6×4,5 film formats are likewise theoretical possibilities, but gaining functional adapters may necessitate some DIY.

Footnotes

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 This, late, version of the Olympia Sonnar uses a 7-blade automatic aperture design (ASB or Automatische Springblende, in German), but earlier manual and preset versions used setups offering up to 18 blades.

⁷ 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).