Data sheet: Carl Zeiss Ultron 50 mm f/1.8

Pekka Buttler, 01/2023


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

Brand:Carl ZeissLens nameUltron 1,8/50
Focal length(s)150 mmAngle-of-view246,8 °
Maximum Aperturef/1.8In Production1968–1972
Lens mountsIcarex BM, m42Subfamily (if applicable)––
Length338,0 mmDiameter461,5 mm (lens barrel)
65,6 mm (breech-lock)
Filter ring diameterN/A (see notesWeight277 grams
Lens element count7Lens group count6
Aperture blades (S/R/C)55 SFocus throw240 °
Minimum focusing distance45 cmsMaximum magnification1:6,9
Has manual aperture ringYESHas Manual focus ringYES

Further notes:
• This lens is legend. In its days (e.g. Popular Photography, 1969), it was considered one of the sharpest standard lenses ever produced.
• Designed by A.W. Tronnier for Voigtländer (see history below), it is the first (and one of only a select few) mass-produced lenses that feature a concave (inward-bulging) front lens surface. According to unsubstantiated legend, Tronnier designed the Ultron in that way simply as an “I told you so” – to showcase that convex front elements by no means was the only way to design lenses.
• ‘Ultron’ is a traditional name used by Voigtländer to designate its large aperture standard lenses, but the other somewhat contemporary Ultrons (such as the 50/2 Ultron for Voigtländer Prominent and the Color Ultron 50/1.8 for Rollei/Voigtländer SLRs) do not share this lens’ design.
• Alike all lenses offered for the Icarex line of cameras, its aperture ring is without click-stops
• This lens does not have a traditional filter ring, and instead offers a bayonet-type connection used for both the Icarex’ typical lens cap and proprietary attachments. On eBay, you can find adapters that modify this bayonet into a regular 52 mm filter thread.

Bayonet front attachment on Carl Zeiss (Icarex) lens (Pictured Skoparex 35 mm f/3.4)

History of Carl Zeiss (Oberkochen)

There are few names in camera optics more illustrious than that of Carl Zeiss. Founded in the German town of Jena in 1846 by Carl Zeiss (hence: ‘Carl Zeiss Jena‘), there are few major developments in lens optics that the company was not involved in during 1846–1945. Names that are even today well-known in optics – such as Planar (1896), Tessar (1902), Sonnar (1929), and Biotar (1939) – were the product of Zeiss’ first century of technological innovation. But as the second world war broke out in 1939, development of consumer optics had to take the back burner…

After the Second World War Germany was divided into a Soviet zone (subsequently: East Germany) and the west-allied zones (subsequently: West Germany). While most Zeiss works resided in Jena (optics and glasses) and Dresden (cameras), which were in the Soviet sector, a contingent of Zeiss managers migrated to a Zeiss plant in Oberkochen near Stuttgart (American Zone) and set up shop in the West 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 Jena and Zeiss Oberkochen were united again, and have since again been at the undoubtable forefront of lens development. After close to two centuries in the optics industry, the majority of Carl Zeiss’ revenue today (and since some time) comes from sources other than camera optics.

This lens harkens to the time of the cold-war and the East/West split. While the photo/optical industry was not given the same ‘National importance’ in West Germany (as it was undoubtedly given in the East), there were many in West Germany who felt that Germany still had something to offer the photographic industry (and should not voluntarily give up to the Japanese onslaught).

History of the Icarex and Zeiss lenses for the Icarex

n.B! all lenses are defined by their history, but this is even more true for the Carl Zeiss Icarex lenses. Hence, I think it worthwhile to spend a bit more time on the discussing the history of this line of lenses.

The end of the 1950s saw a veritable onslaught7 of ambitious, technologically advanced and aggressively priced Japanese SLR cameras. Suddenly the German camera industry found itself no longer being copied, but was instead about to fall behind. This was especially pressing for Zeiss Ikon (the camera manufacture arm of Zeiss). Zeiss Ikon had in 1959 introduced the Contarex system camera – a marvel in both features and technical complexity. Whereas the Contarex was squarely aimed at the Pro segment Zeiss Ikon also offered the Contaflex for the more price-conscious segment. The Contaflex was a leaf shutter camera using a set-lens approach to allow varying focal lengths8. So, on the one hand Zeiss Ikon offered an over-engineered and over-priced marvel, on the other hand a more affordable camera that simply was simply not competitive with the Japanese offering. The stage was set for a fundamental failure, and – to make matters worse – this failure was entirely of Zeiss Ikon’s own making.

In 1956 Zeiss had bought a majority share of the venerable camera manufacturer Voigtländer, but did not really know what to do with this new acquisition. It was not that Voigtländer designs were bad – far from it – but Zeiss’ decision-making was burdened by the not-invented-here-syndrome. So it came that when Zeiss Ikon in 1959 was confronted with the Voigtländer 132 prototype – a sleek, interchangeable lens camera with TTL-metering and modular viewfinders – they did nothing with it. Two year later, that concept had been honed into the Voigtländer Bessaflex prototype9 – a camera that would have sat perfectly in the Zeiss Ikon lineup, was technologically on par with the Japanese competition and could have been offered at a highly competitive price, and Zeiss Ikon management again dawdled. It would seem that they were worried that the new camera would not only obliterate sales of the Contaflex line, but that – at roughly a third of the price – would also challenge the Contarex – the nominal King of the Zeiss Ikon offering.

After several years of procrastination, the new concept was in 1966 finally unveiled as the Zeiss Ikon Icarex. And while the first–mover advantage that was Zeiss’ for the taking had been lost to procrastination, the Icarex might well have given the Japanese a run for their money, had Zeiss Ikon’s management not made their utmost to make the Icarex into a case example of how not to…

First, instead of using the years in between to up-to-date the original Bessaflex design, the Icarex was launched largely in accordance with the early 60s specifications (minus TTL metering), and instead of adopting the modern and sleek Bessaflex design the Icarex was restyled into another heavy, Zeiss Ikon brick. Second, the Icarex was launched with a specialised proprietary mount – the Icarex ‘bayonet’ mount – meaning that there was no base of readily available lenses (and that Zeiss had one more mount to support). Third, potentially because of the Icarex’s not-invented-here origins, Zeiss Ikon did not market the system aggressively (in fact, quite the opposite).

Fourth – in what fundamentally constituted the system’s coup-de-grâce Zeiss Ikon was unbelievably slow in introducing lenses for the Icarex mount. From launch and during the critical first two years of the system, only three lenses were made available: two standard lenses (a 50/2.8 ‘Tessar’ and a three-element 50/2.8 Pantar), and an f/3.4 90 mm lens. In short, the Icarex’s launch was crippled by a set of low-grade lenses. This is all the more unbelievable considering that Zeiss Ikon not only had the entire catalogue of Zeiss designs to draw from, but could have also used Voigtländer’s lens portfolio.

Admittedly, 1968 saw significant improvement: Firstly, instead of only offering the Icarex with the proprietary ‘bayonet’ mount, also a thread mount (m42) body was introduced10 (one more mount for Zeiss to manage), but 1968 also saw the introduction of a spate of long-awaited lenses, including a 35 mm wide-angle, the legendary 50 mm f/1.8 Ultron, a lineup of longer Tele lenses (135–400 mm) and even an f/2.8 standard zoom (!). Most amazingly, except for the Ultron, all these lenses were existing Voigtländer designs11 that would have been available already in the late 50s/early 60s.

But by 1968, whatever chances Zeiss Ikon might have had to meet the Japanese challenge were long gone. Frank Mechelhoff refers to the Icarex as the tragic hero of the (West) German camera industry – the hero who, in spite of virtue and character – was destined to fail. In the case of the Icarex’ failure it was Zeiss Ikon management who through either sedateness, stupidity or spite missed their golden opportunity and showed that Zeiss Ikon was unwilling to do what had to be done to challenge the ascendant Japanese camera makers.


This lens exists in two optically identical variants, one of which sports an m42 mount, and the other offers an Icarex bayonet mount.

Adapting (Icarex-version)

This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a Zeiss Ikon Icarex body with a bayonet mount. Even though the Icarex never was a smash hit, it has shown itself to be a sturdy design and while you’re unlikely to stumble upon them at a garage sale, acquiring a functional Icarex body online is not really a challenge.

Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable adapter. Moreover, a simple ‘dumb adapter’ will do the job perfectly. As the Icarex mount was never popular, availability of Icarex adapters to all mirrorless mounts cannot be taken for granted. On the other hand, one can daisy-chain adapters (e.g. Icarex->Canon EF; Canon EF –> mirrorless) which also opens up a wide range of special adapters (speed boosters, helicoid adapters, tilt/shift adapters).

Using Icarex bayonet mount lenses on dSLRs can also be an easy option, depending on which dSLR.
• Canon EF has the shortest flange focal distance among full-frame dSLR’s and Canon’s wide range of dSLRs are able to mount Icarex bayonet lenses perfectly using a simple adapter ring.
• Sony/Minolta A, Pentax K and Nikon F dSLRs are not even in theory able to use Icarex lenses without an adapter that uses corrective optics to allow infinity focus. Due in part to the relative scarcity of Icarex bayonet lenses – such adapters are very rare (I’ve seen such adapters, but at the time of writing, cannot find any).

Adapting (m42-version)

This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need an M42-mount film body. Luckily there are a lot of those available.

Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable adapter. Moreover, m42 lenses are so uncomplicated that a simple ‘dumb adapter’ will do the job perfectly. Moreover, due to the popularity of the m42 mount, special adapters (helicoid adapters, tilt/shift adapters) are readily available. Alternatively, one can choose to daisy-chain adapters (e.g. M42->Canon EF; Canon EF –> mirrorless) which also opens up a wide range of speed boosters .

Using m42 lenses on dSLRs can also be an easy option, depending on which dSLR.
• Canon EF, Minolta / Sony A and Pentax K dSLRs are able to mount m42 lenses perfectly using a simple adapter ring.
• Nikon F dSLRs have a long flange focal distance, meaning that mounting m42 lenses needs an adapter that uses corrective optics to allow anything close to infinity focus.


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, 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 companies was given freely to everyone (the western 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).

7 Some key introductions: Asahiflex (1952); Miranda T (1955); Asahi Pentax AP (1957); Topcon R (1957); Minolta SR-2 (1958); Yashica Pentamatic (1959); Nikon F (1959); Canonflex RM (1959); Petri Penta (1959); Konica F (1960)…

8 The base lens of the Contaflex was a 50 mm f/2.8 Tessar, the front-part of which could be exchanged against other front-elements (“Pro-Tessar”) allowing either a 35 mm f/4; 85 mm f/4 or 115 mm f/4)

9 Not to be mistaken for the 2000s Cosina-made Voigtländer Bessaflex TM.

10 Icarex bodies would hereafter carry either a badge saying TM (thread mount, m42) or BM (bayonet mount, Icarex). Icarex bodies that do not carry a badge are early bayonet mount versions.

11 Indeed, what is remarkable about the line of lenses that Zeiss offered for the Icarex mount, is that all the lenses (with the exception of the 25 mm f/4 Distagon introduced in 1972 as a dying gasp) actually are Voigtländer designs, manufactured at Voigtländer’s Braunschweig plant. This can partially be seen by that the lenses carry Voigtländer’s classic lens names (Skoparex; Pantar, Ultron, Dynarex, Super-Dynarex, Telomar and Zoomar), but looking at the schematic of the lenses, it becomes clear that even the Icarex ‘Tessar’ actually is a Voigtländer Color Skopar.