Carl Zeiss Ultron 50mm f1.8 is a lens for short-lived Zeiss Ikon Icarex line of cameras. Famous on the internet – it generally has good reviews and recommendations, so I wanted to try it for myself. It turned out to be one of my favourite vintage lenses. I use it a lot, taking it on trips to the mountains, forests, or just casual strolls in the park.  I also bought an M42 version too for comparison.

It’s difficult to pinpoint what makes the images captured by it so appealing. The resulting images have a unique rendering which is something difficult to express in words. The lens design is equally different; it uses a concave front element which is rare in lenses. 

This excellent review has dispelled the myth that this lens is better than newer lenses. Modern lenses beat this lens in pure sharpness, coma suppression, flare resistance, but this lens delivers a bucketload of vintage style, with which current well-corrected lenses cannot compete. 

Carl Zeiss 50mm f1.8
Carl Zeiss 50mm f1.8

Details & History

Albrecht W. Tronnier designed the Ultron 50mm f1.8 while working for Voigtländer AG, which filed the patent US3612663 for this lens design in 1969, and had it approved in 1971. After a short run, in 1972 the lens production ceased. Carl Zeiss (which owned Voigtländer) only made a few thousand lenses in Voigtländer plant, West Germany, which makes them quite rare. 

Lens diagram for Ultron 50mm f1.8 taken from the patent application

“Within this primarily Gauss type of double objective is the new system of the invention which in contrast with known techniques has a new type of forward component which terminates at its front end in an end surface which is not convexly curved in a forward direction toward a distant object so as to have a positive front end surface but instead has forwardly directed toward a distant object a concave front end surface which is dispersing and which in addition acts in an overcorrecting manner with respect to image errors.” – A. W. Tronnier et al.

This particular lens design makes it a unique and exciting lens to own for collectors and photographers alike. No other lenses utilise the same optical formula. Color-Ultron 50mm f1.8 succeeded this lens and was designed by Dr Erhard Glatzel. It had a slightly convex front element, as opposed to concave glass element present in this lens.

Carl Zeiss Ultron 50mm f1.8 Specifications

Focal length: 50mm
Aperture f1.8 – f16
Mount: Icarex BM / M42
Construction: 7 elements in 6 groups
Minimum focus distance: 45 cm
Focusing: Manual
Number of diaphragm blades: 5
Radioactive: No
Production run: 1968-1972
Made in: West Germany by Voigtländer for Carl Zeiss

With original cap and rubber hood
With original cap and rubber hood

Construction

Carl Zeiss Ultron 50mm f1.8 is a robust lens. The barrel and internal mechanisms are metal. It has survived for over 40 years of use and still performs well with a smooth and pleasant focus. There are five aperture blades, controlled by a step-free aperture control ring, which can be a bonus for videographers. 

Carl Zeiss 50mm f1.8 Mount
Carl Zeiss 50mm f1.8 Mount

For those with a physics interest — I have tested the lens for radioactivity. For better or for worse, I found that it does not contain any radioactive glass elements. I wonder how it would perform if it had some thoriated glass and multicoating. One can only dream.

The minimum focus distance of 45cm is quite beneficial for good closeup shots. 

Minimum Focus Distance
Minimum Focus Distance of 45cm

Versions

There are two versions of the Ultron — Icarex BM and M42. The M42 mount version is the latest and a more expensive model. They have the same optical formula, minimum focal distance, and other parameters. I have both versions and can’t see any differences in the images between the two.

I would buy the Icarex BM version because it is cheaper, but ensure that there is an appropriate adapter available for the camera body. 

Carl Zeiss 50mm f1.8
Carl Zeiss 50mm f1.8

Size and weight

Carl Zeiss Ultron f1.8 is quite small compared to other lenses and is easy to carry even with an adapter, and balances well on the camera. It does not feel light or flimsy when holding it and weighs 185 grams. 

Price

It is on the expensive side, usually going for over £300 for a good quality Icarex BM sample (€350 / $400). M42 version can be up to £100 more. Limited production numbers and unique design makes this lens quite collectable. I luckily bought mine on eBay, so if you are interested, take a look

Compatibility / Adapters

The Icarex BM version was troublesome to adapt to my Canon EOS R. I bought a Kipon ICA35S to EOS R adapter but found that it does not depress the aperture pin on the lens, thus making aperture stuck open.  A significant problem with this particular adapter, so I would not recommend it for this lens.

I then tried an Icarex 35S to Canon EF adapter from eBay, which had a lip that depresses the pin and allows the aperture to work. However, when mounted on EOS RF to EF adapter, it shorts the contact pins and causes the camera to lock up. 

A little bit of duct tape (or any other non-metallic strong sticky tape) solves the problem – stick the tape on the adapter where the contacts touch it, and it will no longer short circuit the camera. I am glad my EOS R still functions after being short-circuited, so be warned.

M42 version has no such problems, as it works just like any other M42 lens, and there are plenty of adapters for the majority of camera mounts. 

Image Quality

It is purely subjective, but I like the images this lens takes. They have that beautiful 3D look to them. There is enough sharpness wide open (if the subject is right). When stopped down this lens is as good as modern lenses – sharp, contrasty, and with pleasing colours.

F1.8 – Somewhat sharp in the centre, but soft overall, with loss of contrast. Good for portraits.
F2.8-4 – Sharp and contrasty in the centre, improved sharpness in the edges.
F5.6-F8 – Everything is sharp and contrasty.
F11 and smaller – No improvement, starts to soften due to diffraction

Pros

  • Photos are sharp and have a unique character
  • Lightweight
  • Unusual lens design
  • Robust metal construction
  • A great tool for artistic photography

Cons

  • Expensive
  • Poor flare suppression
  • Difficult to find 
  • Difficult to find a suitable adapter for Icarex BM version

Conclusion

Carl Zeiss Ultron 50mm f1.8 is a pleasure to shoot with, and I will never sell it. It played an essential part in the history and evolution of Zeiss lenses and was designed by a legendary lens designer.  It’s very versatile as a walkaround lens. The only issue I had was finding an appropriate adapter and tweaking it to work correctly.

I would give an overall rating of 5 out of 5.

What was your experience with this lens? Please comment below!

Sample Images

Wide open at f1.8
Wide open at f1.8
Evening in Austria
Stopped down to about f4
This lens flares very easily
Stopped down to f2.8
I actually like this flare
Stopped down to f2.8
Picture of a plant
Wide open at f2.8
There are only 5 aperture blades
Five aperture blades visible in out of focus highlights
Japanese pear at minimum focus distance
At minimum focus distance
Objects appear to pop out of the picture
Stopped down to about f2.8
On a trip to Germany
Stopped down to about f2.8
On a trip to Wales
Stopped down a little
Girl with snow in the hair
Stopped down to f2.8
On a trip to Liechtenstein
Stopped down to f4
Stopped down to f2.8
Stopped down to f2.8
Watch out for the flare
Very prone to flare

16 Replies to “Carl Zeiss Ultron 50mm f1.8 Lens Review”

  1. Very nice review. I has been wondering whether to buy or not to buy given the price is relatively expensive (Similar price point compare to Leica R 50-Cron btw). After reading both sides of reviews, I decide to buy it. (Just finalise the purchase transaction.) That completes my M42 Zeiss-Voigtlander trio collection of Skoparex 3.4/35, Ultron 1.8/50 and Super-Dynarex 4/135.

    1. Amazing! Please let me know what you think of the lens when you get it! Now I want to try the Skoparex 3.4/35, and the Super-Dynarex 4/135 🙂 Thank you for your comment, means a lot to me.

  2. My dad bought a Zeiss Icarex 35S in ~1971 with the Ultron. I bought it used from him ~1975, and have had it since. It went through a period of non-use for 25-30 years, but I have pictures from the 1970s/1980s and today. I have rediscovered the lens, and really appreciate the rendering. At the time I first bought it, I thought it was a good lens (it was a Zeiss), but it did not have the kind of reputation it has today. I am glad I kept it!

    Here are some shots (old and new) taken with this lens:

    https://www.flickr.com/search/?user_id=157638541%40N07&view_all=1&text=zeiss%20ultron

  3. I bought this lens from my dad in 1975. I used it for many years, then put it away for many years, reviving it 2 years ago. I really like the way it renders, and am glad I kept it. You can see some Ultron shots from long ago as well as today on my Flickr account (linked as my website).

    1. Hi Mark, thank you for your contribution! Yeah, it does have a unique rendering – which I also really like. It has also dramatically shot up in price recently. It seems more people are starting to appreciate it more now 🙂

  4. Thanks for your nice review.
    I have the ultron 50mm as well as the skoparex 35mm BM version. However, they caused twice (a few years between) a short circuit on my Canon 5D. I have not used both lenses since… Which contact pins should I block with the duct tape, or do you mean all contacts…?
    Best Regards,
    Leendert

    1. Thank you for your comment! I did stick the duct tape on pretty much the whole “end” of the adapter, as it rotates and shorts all contacts in the process. With the adapter masked, there is no issue with shorted contacts. The trick is not to block the pins themselves but to make the adapter non-conductive. That way if you take off the adapter, you can put another lens on and it will work just fine.

  5. I congratulate you fo this excellent review. You sensibly mix anecdotes with history and practical descriptions. I don’t pay a lot of attention to lab tests and benchwork measurements (although I do possess some knowledge in optics). I’m an old man of 65 and have been an amateur photographer (courtesy to my late dad) for almost 60 years. My renewed interest in vintage lenses started two years ago and I possess … far too many ! The M42 Ultron, together with an Hexanon 57 mm, are my most « precious » (= pricy) ones. Reason for buying it was : a decent price (vendor and I do often business together) but above all … the concave front element. I know it is silly but all decisions needn’t be reasonable. You word it perfectly well : it is difficult to describe its « plus » in precise photographical terms. I have the feeling to be « present » when I watch pictures taken with it. You’re not just an innocent by-stander. You are « part » of the picture. It is similar to loud-speakers you like : they render live music, not just a perfect sound. Note : alpha 7 is « plans for the future » but money is short. I presently use an OM-D, an old E-520 and a Nikon D7000, nothing very posh. The Ultron does equally well with the three of them, even though the infinity lens spoils its « Leistung » (= performances) at wide apertures on the APS-C.

    1. Thank you for your input Charlier, your words mean a lot to me! Is the Hexanon 57mm an f1.2? I also really like that lens, but haven’t got time to write about it yet.

      1. Actually, I work with both Konica’s 57 mm lenses. Strangely, I had the f/1.2 first (my sole “very fast” lens) and acquired the f/1.4 shortly thereafter. The “big boy” is great, but I find it risky to take around with me too often and it is a weight to carry as well. Plus: there is an embryonic collector in me to be frank (but not the sinews of that war ….).

  6. Again brilliant review, including history that I love, about one of the best lenses ever made. Thank you.

    1. “One of the best lenses ever made …”
      I feel like writing this sentence (sounds as a judgment as well) every time I’m using yet another lens! We were brought up, I’m afraid, in the Western world, to compete, to win, not the be a “loser”. Fortunately, it is also a testimony to our enthusiasm, to our joy and pleasure after taking pictures (all types) with a specific lens. I do possess at least FIFTY “best lenses”. Yet, the Ultron is almost my most expensive lens and I’m not sure it is 10 times “a better lens” than a Helios-44 or a Lydith 30 mm, let alone 5 times a better lens than most Mamiyas, than a Zuiko 100 mm, than …. You see what I mean. But the Ultron is “special”, in the same way as the Hexanon 57 mm f/1,2 is special or the Jupiter-9. Most comments on this blog seem derived from readers with a passion, a “devotion” to amateur photography.
      “That’s the way, uh-huh, I like it!”

  7. Read this paper for the second time today, and the allusion to Skoparex and Super-Dynarex 135. I possess those in Icarex-mount (and a 50 mm Tessar as well). The adapter to MFT is a Kippon one, very tight but I think a little bit too long. The Sk and Tes don’t reach infinity, the 135 mm does (?). Normally, they make them a bit short and you get “overshooting”, don’t they? Fortunately, I also have a DKL-Skoparex (very practical, even on Nikon WITHOUT infinity lens, good thing), a DKL-Super Dynarex (beautiful, almost a piece of jewelry for no money at all) and pfff, at least a dozen Tessare (German plural with an -e) in various mounts. This Skoparex is every bit as good as what people say, a dream of a lens with great colors. And the DKL system is FUN to use, with as a bonus the silly little mobile depth-of-field indicators. They serve no purpose whatsoever but are cute! My Icarex Tessar is about the worst I have but its mechanical build is wonderful. And the tele-lens is very good, without any difference between both versions. Mind you, I never shoot charts. I’m 65 years old, semi-retired and most of my free time (and pocket money) goes into taking pictures, out in the field. All my judgments are therefore very subjective. I’m not an addict of sharpness for the sake of sharpness. I really do believe lenses have got a personality (not a psychological one of course), a pattern which is secondary to their physical properties and which
    influences the overall balance of a shot. For instance, the Enna (München) wide-angle lenses seem to evoke hatred in most. I LOVE them … I leave it at that for he time being.

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