Pekka Buttler (Updated 8/2026)
Icarex BM mount specifications
Mount type: breech-lock (ring on lens)
Flange focal distance: 48 mm
Film format: 36mm x 24mm (‘Full frame’)
Mount communication: Aperture stop-down pin (body-to-lens communication)
Identifying the Icarex mount?
Key characteristics of the mount of Icarex BM lenses:
[1] Breech-lock ring with two openings of different sizes
[2] Breech-lock registration pin (always aligned with lens top)
[3] Aperture stop-down pin
[4] Cover for spring and steel ball (see reader comment below).
Note! The rear of Icarex BM lenses typically (based on four lenses) have very prominent slot-screw heads, but their number and spacing is not a definite characteristic.
Information on the Icarex BM mount:
The Icarex BM (for “bayonet” mount) was introduced in tandem with the Zeiss Ikon Icarex 35 camera in 1966. The story of the Icarex camera and “bayonet” is a sordid tale of how – in some rare cases – companies have a technologically competent product, but still manage to do everything wrong. In short:
• Zeiss Ikon was worried about the Icarex eating into sales of their other products (Contarex and Contaflex). Hence, the Icarex was crippled and repeatedly delayed until it was obsolete at launch.
• Only three lenses were offered for the Icarex at launch, and two of those were different 50/2.8’s (a four element ‘Tessar’ and a three element ‘Pantar’) and it took another two years before Zeiss Ikon launched anything wider than 50 mm and anything narrower than 90 mm (even though the designs were available).
• The Icarex was initially launched without any built-in metering, even though the major competition offered integrated metering (and was able to sell well due to this). Integrated metering capability was added to the Icarex only in 1969.
• After launching the Icarex, Zeiss Ikon had one more mount to support. This was partially due to that …
• The Icarex was not originally a Zeiss Ikon design. Instead it was a design Zeiss Ikon inherited from Voigtländer (Zeiss Ikon had acquired Voigtländer earlier). The not-invented-here element probably contributed to Zeiss Ikon’s lacklustre effort in pushing the Icarex.
• Almost of all lenses manufactured in Icarex BM mount (under the ‘Carl Zeiss’ brand were rebadged Voigtländer lenses1. Even the BM mount 50/2.8 “Tessar” was actually a Voigtländer Skopar. As such this is not a bad thing (Voigtländer was an optics pioneer), but shows how the Icarex was to be the unwanted stepchild.
• As sales were disappointing, Zeiss Ikon launched a parallel series of Icarex cameras with m42 thread mount in 1969. Subsequently, Icarex cameras would be either “TM” (m42) or “BM” (Icarex). (Any Icarex cameras without a “TM” badge are “bayonet” mounted)
• To add insult to injury, the Icarex “bayonet” mount is actually a breech-lock mount (which is why I’ve parenthesized “bayonet”).
And if you think this sounds too unbelievable to be real and you’re convinced I’m tripping, at least I’m not tripping alone.
As such, this sorry story is indicative of the miserable end-game of the (west) German camera industry. While many like to portray this tale simply as a “could not compete against cheaper asian labour” -story, it is actually a story of arrogance, incompetence, infighting, and chronic indecision. Maybe I’ll tell my take (the management scholar’s version) one day. In any case, all this resulted in that the Icarex BM mount was officially discontinued in 1971, after only 5 years.
Carl Zeiss / Voigtländer lenses for the Icarex system
The table below summarises available information on the lenses that were manufactured under the Carl Zeiss brand for the Icarex system
| Name | Years | Optical design | Origins | BM | M42 | Notes |
|---|---|---|---|---|---|---|
| Distagon 25mm f/4 | 1972 | 7 elements | New Zeiss design | no | yes | |
| Skoparex 35 mm f/3.4 | 1968–72 | 6e / 5g | Old Voigtländer design (Bessamatic) | yes | yes | [data sheet] |
| Ultron 50 mm f/1.8 | 1968–72 | 7e / 6g | New Voigtländer design | yes | yes | [data sheet] |
| Tessar 50 mm f/2.8 | 1966–72 | 4e / 3g | Old Voigtländer design (Bessamatic) | yes | yes | [data sheet] |
| Pantar 50 mm f/2.8 | 1966–72 | 3e / 3g | Old Voigtländer design (Bessamatic) | yes | yes | [data sheet] |
| Dynarex 90 mm f/3.4 | 1966–72 | 5e / 3g | Old Voigtländer design (Bessamatic) | yes | yes | |
| Super-Dynarex 135 mm f/4 | 1968–72 | 4e / 3g | Old Voigtländer design (Bessamatic) | yes | yes | [data sheet] |
| Super-Dynarex 200 mm f/4 | 1968–72 | 5e / 4g | Old Voigtländer design (Bessamatic) | yes | no | [data sheet] |
| Telomar 400 mm f/5 | 1968–72 | 3e / 2g | Old Voigtländer design (Bessamatic) | yes | no | |
| Zoomar 36–82 mm f/2.8 | 1968–71 | 14e / 11g | Old Voigtländer design (Bessamatic) | yes | no |
Adapting Icarex BM lenses:
Thanks to the relatively forgiving flange focal distance (48 mm) of Icarex BM lenses, there are few theoretical or practical impediments to adapting these lenses – both to dSLR’s and mirrorless cameras.
On the other hand, due to the relatively meagre installed base of these lenses, third party adapter manufacturers have not been too eager. Resultingly, while adapters exist, only some mounts are covered. Furthermore, dedicated Icarex BM speed boosters (for owners of APS-C bodies) do not exist. Hence, should one want to speed boost an Icarex BM lens, one needs to find a suitable combination of adapter ring and speed booster.
Once an adapter has been acquired, the use of Icarex BM lenses on MILC is very straightforward. Furthermore, the 10 Icarex BM lenses manufactured by Zeiss/Voigtländer are of the highest build quality, and while usability-wise some of them may be considered somewhat quirky (even medium tele lenses like the 200/4 Dynarex have a very narrow focus ring), their build quality is second to none. Furthermore, Zeiss/Voigtländer Icarex BM lenses are devoid of click-stops (which some will appreciate).
But, you might ask, why give a flying fig about a lens mount that only ever offered ≈10 in-house*2 lenses, many of which were later also made available in M42?
Three reasons, and only the last one really matters:
– First, and I acknowledge that this might be very personal, but for me dabbling with legacy lenses goes hand in hand with a morbid interest in the history of photographic machinery, and due to this, I admit to having a fascination towards the death-throes of a pair of companies (Voigtländer and Zeiss Ikon) that were once trailblazers of the industry.
– Second, the fact that M42 is one of the most popular lens mounts of all time, does not make it a good system (in the technical sense). Personally, if I was offered the same lens in M42 and Icarex mounts and handed a pro-level adapter for both, I would gladly go with Icarex any day.
– Thirdly, While none of the ‘Carl Zeiss’ -branded lenses for the Icarex system is a real dog, there are a number (if you’re being critical then two; if you’re in a really foul mood then only one) of lenses offered for the Icarex system that shine: The 35/3.4 Skoparex and the fabled 50/1.8 Carl Zeiss Ultron3. And while the Ultron was also available in M42, (last time I checked) the price difference between the average Icarex and M42 Zeiss Ultron sales was sufficient to justify the investment in a pro-level Icarex-NEX adapter 10 times over.
Footnotes:
- For those in the know, the nomenclature of Icarex lenses are a dead giveaway, as they typically combine the name ‘Carl Zeiss’ with classic Voigtländer lens names (e.g. ‘Skoparex’, ‘Ultron’, or ‘Dynarex’). ↩︎
- I am here only talking about the Zeiss/Voigtländer lenses for the Icarex Bayonet mount. However – while the Icarex system was relatively unsuccessful, the limited set of lenses offered for the mount also contributed to that several third party manufacturers (most prominently both Soligor [company profile] and Vivitar [company profile] manufactured adapters for their T4/T-4 intermediate-mount systems (As noted by a friendly reader) ↩︎
- In the dying days of the Icarex system, Carl Zeiss also introduced a 25 mm f/4 Distagon (incidentally, the only Icarex lens that was not a Voigtländer design), but as it was introduced only months before the entire system was discontinued, it was made available only in M42 mount and it is extremely rare (only some tens of copies according to one source). Hence it is not noted here. ↩︎
Hey Pekka,
I got my hands on an Icarex-mount camera and lens recently, and I can state with absolute certainty that [4] Thingamajig is just a cover element / pressure plate. Underneath, it is hiding a spring and a steel ball. It’s there to provide the breech-lock locking ring with a clicking sensation similar to how it’s done in aperture rings (which is something that Icarex lenses don’t do, by the way! Cue jokes about German engineering…). It provides only one click, though, stopping the ring in the “open” position; so it’s basically a 4-component (screw, metal bit, spring, steel ball) way to solve a problem that could be easily solved with one (say, a screw and shaping the detail underneath to provide a hard stop). Cue jokes about German engineering, again.
If you want photos of this wondrous contraption, I can send them to you by e-mail but it’s really nothing special 🙂
Also, Soligor offered a T4 adapter in Icarex BM. I have not seen it mentioned in any Soligor literature or magazine reviews, but have seen two for sale on eBay.
Thank you, Pekka for shedding some light on the little known Icarex system and lens mount. I bought my Icarex 35S in 1970 or -71. A grave mistake as it was immediately discontinued and, until the emergence of ebay, I could not even buy filters for it. Within its limitations it was a nice camera though with such features as a built-in viewfinder blind, an external meter needle and a judas window to show the aperture in the viewfinder. Regrettably it developed shutter problems a few years later. I had, and still have, the Tessar 2.8/50, Skoparex 3.4/35 and Super Dynarex 4/135. Good lenses, but slow. I later inherited my father’s two Icarex 35 CS and with them the legendary Ultron 1.8/50.
I can confirm that indeed it was a Soligor T4 adapter for the Icarex lens mount. I have two of them. There is also a very strange, and in my view sad, phenomenon in connection with the T4 mount. At least three times I have seen on German ebay lenses that are clearly recognizable as Soligor T4 lenses but equipped with Zeiss Ikon name rings. There is in fact one such 135mm lens on German ebay right now: Zeiss Ikon BM 135mm F2.8 Icarex BM | eBay.de . I’m almost sure I have also seen one such 35mm lens. The only explanation I can think of is Zeiss Ikon desperately trying to keep up some sort of customer support after the end of Icarex production and making an arrangement with Soligor. Keep in mind that genuine Zeiss lenses for Icarex are labeled Carl Zeiss, not Zeiss Ikon, Carl Zeiss being the lens manufacturer and Zeiss Ikon the camera company.
A little-known fact about Icarex lenses is that the shorter focal lengths (35-90mm) had a “filter thread” up front in addition to the B50 filter mount. It is the knurled ring on the outside front of the lens barrel. It is in fact a male 56mm thread. There was a rubber lens hood with a female thread to match. I have two of them. It was possible to mount and dismount B50 lens cap and filters without removing the lens hood. A nice system. There were no 56mm filters to match in the Icarex system. I don’t know if there are third party 56mm screw filters, but it’s not a common size. I would also like to point out that in the range of B50 supplementary lenses there was one with a focal length of 2m. Very unusual, but nice to have as it makes the 135mm lens much better for portraits, letting you undercut the MFD of just under 1.6m by a very useful amount. I’ll also point out that the Icarex B50 mount is not the same as Hasselblad B50.
The big, slotted screws on the rear face of the Icarex lenses have, as far as I can tell, something to do with adjustment of the automatic aperture mechanism. I have got two Super-Dynarex 4/135mm lenses. One has four of these screws and one (the older one) has three. Both lenses have problems with the aperture. The mechanism is rather flimsy and not well constructed, I think.
I recommend trying out the Icarex lenses. They are optically good, and you don’t know what superb build quality means until you’ve handled one.
Hi Andreas,
and thank you for your detailed comment. I have an Icarex 35 CS camera (with unreliable metering, off course) as well as a broad set of lenses. I’ve made some nice pictures with it.
While I have not compared the Icarex to the contemporary Contarex, I think it was a more than decent product and might even have been competitive if Zeiss Ikon had gone all-in on the system as soon as they acquired it as part of Voigtländer. Instead they dithered. And the rest is history.
Very interesting about that Soligor ‘Zeiss Ikon’ lens. I too found it on ebay. Given the serial number on that lens, that would mean that there were once Tokina-made lenses carrying the name ‘Zeiss Ikon’ on their name rings. I do not know what I think of that, but I’ve certainly seen similarly odd things out there.
Kind regards,
Pekka