Here, at Skyllaney Opto-Mechanics, we have an affection towards Sonnar formula lenses, and we see the desire of our clients to experience these wonderful lenses for themselves. Because of that, we work on entirely restoring classic Contax I and Jupiter 8 lenses.

The Soviets, as a matter of spoils of war after WWII, took the large majority of the Zeiss factory back to Russia, which included many machines, jigs, assembly lines, technical drawings and workers.  The Soviets then began to sell the Zeiss lenses at first under the ZK lens brand, and in the early 1950s, the ZK branding became Zorki by KMZ.

These early ZK and Zorki lenses are typically Zeiss optics and Zeiss mechanics that were taken as war reparations.  In the mid-1950s, the Soviets performed a mild re-computation to the 1937 5cm f/2 Sonnar formula, which primarily involved truncation of the element diameters to save on glass material at the expense of mild vignetting and slight wide open corner sharpness.

Most issues with poor image quality of the Jupiter 8 lenses that are mentioned on the web, stem more from worn assembly mechanics, mis-calibration and the abuse it may have sustained over its lifetime.  Our upcoming ‘Big Sonnar Review’ sheds light on this, where we found that a well-adjusted Jupiter 8 lens, often matches and even exceeds the Zeiss-Opton Sonnar’s from the 1950s. The bigger issue seems to be getting a well-adjusted Jupiter 8, coupled with the fact that they arent made at all, being a product of the Soviet Union.

At Skyllaney Opto-Mechanics, we have had hundreds of 50mm Sonnar lenses come through, and have acquired a significant pool of spare Sonnar parts now. About 100 or more of these have been ZK/ Jupiter 8’s in there various incarnations from 1948 through the1980’s. This is one lens, where the optical formula from about late 1954 to their end of life, had gone though a near endless series of changes to their mechanics.

We take the best of the best and do a full restoration to bring for sale classic 50mm Sonnar lenses for use on LTM and M film and digital cameras.

All the lenses are disassembled and cleaned in our ultrasonic cleaning vats.  Oxidation and other impurities are removed during this process.

The mechanical lens parts then undergo a multi-stage polishing and buffing process, where they are brought to mirror-like finishes.  Tolerances are checked on the parts to ensure accuracy using Mitutoyo measurement equipment, known to be the best measuring equipment in the industry.

The lenses often undergo modifications to allow a new minimum focus distance of 0.85m, instead of their stock 1m.

The mechanics are then assembled, using an ultra-fast synthetic focusing grease imported from Japan.

We then add our custom finger tab, attached permanently to the focus ring, if the customer should desire it. New font colouring is sometimes added as well.

Lastly, we add a custom-matched LTM to M adapter to all our Sonnar Resurrections, which ensures the DOF arrow faces upward at 12’oclock as best we can.  An issue with many LTM lenses is that their starting M39 thread is often not exactly where it should be due to tolerances.  Using an adapter to mount the lens onto say an M6, may cause the DOF scale arrow to be at the 11:00 am or 2:00 pm position because of this.

We try to eliminate this tolerance issue, by matching an LTM to M adapter to the lens, that corrects this tolerancing factor.

On the optical side of these lenses, any elements that have scratches, typically are rejected.  We seek to pull together the objective, front and rear triplet into a set that provides excellent sharpness and performance.

These are then placed into an optical housing.  The aperture is clean and debris free as much as possible.  As most Contax and their clone Sonnar lenses have click-less apertures, we purposely use a thicker grease in the aperture ring compared to the focus ringtone to prevent accidental movement of the aperture ring while focusing.

The optical housing with Sonnar elements and aperture is then installed into these resurrected body mechanics, and then we perform further centring or focal length optimisation.  Once we are sure we are within the comfortable tolerance zone of floating near 51.6mm, we then work on calibrating the optical stack to marry up with the lenses rangefinder cam.  Digital collimating is then done, which checks the German-made split prisms driving the rangefinder patches against a live feed from a full-frame digital sensor. The lens is tested under these conditions at infinity, minimum focus distance and certain key distances in between.

Once the lens passes our inspection criteria, a calibration certificate is generated which accompany all lensed we sell.

Please be aware, nearly all Jupiter 8 and classic Sonnar lenses sold on popular auction sites, have not been serviced, calibrated and restored to these levels.  Often, they have the same grease in them the Soviets first used at the time of assembly, and they have merely been sprayed with WD40 or some other lubricant to get them going again. This is not a long term fix for these lenses in any way.

Additionally, most of the lenses are not calibrated to work on Leica rangefinder cameras and retain the stock Contax calibration standard. It means these lenses, when mounted on Leica cameras, will not focus accurately!  The process to collimate these classic Sonnar lenses to work on Leica can be done two ways.

The first is using a trial and error method, making adjustments and placing the lens onto a film camera, where frosted glass is used at the film plane with a loupe to check for sharpness.

We do not employ this method.  While it might be okay for high grain ISO film purposes, it does not withstand the scrutiny nor lend itself to the ultimate determination of critical sharpness cameras like the Leica M9, M240 and M10 will reveal with their 18-24mp full-frame sensors.

Our digital/ split prism calibration method ensures the critical sharpness of the lens is exactly where the rangefinder thinks it should be. We then verify this calibration, using a digital full-frame Leica M camera to ensure what we focus on, is indeed critically sharp wide open, not merely almost there.

Aside from Skyllaney Opto-Mechanics, the only other engineer we are aware of that can customise and service Sonnar lenses to this detail is Brian Sweeney in the United States.

Much of what we initially learned years ago about Sonnars comes from Brian, and his early Sonnar conversion work has been an inspiration for our line of ‘Resurrected Sonnars’ in our store.

Check our store for our current range of Resurrected Sonnars:

1 Comments on “Sonnar resurrection”

  1. I’m very proud that Skyllaney has taken up this work for rebuilding Jupiter lenses to focus properly on the Leica, and for converting Carl Zeiss Jena Sonnars to Leica mount. Sonnar formula lenses have a unique blend of “perfect imperfections”, something that has been bred out of most modern lenses.
    I no longer work on these lenses, and am very happy that a professional shop is now doing this. I’ve referred Skyllaney to several people, all have thanked me for the it. The work is superb.

    Like

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