Searching for the Tenax III

Page 1 of a British patent application from 1936

It has been known since the 1980s that Zeiss Ikon intended to produce a Tenax III with a built-in meter similar in principle to the Contax III.

Larry Gubas’ presentation of a patent drawing on Facebook for a light meter contained within a camera body is evidence of the changes Zeiss Ikon was considering for its various 35mm cameras. What I find interesting is that the camera type that appears in the drawings is definitely a Tenax of the Tenax II type, and not a Contax. This suggests that Zeiss Ikon intended to build the same metering system into both its Contax and its Tenax.

The evidence in the drawings: the proportions of the body, the placement of the rangefinder windows and the square viewfinder window are all pure Tenax. The shape of the lens and placement of shutter and focus levers are also Tenax. There is no way that this camera could be a Contax. But what about the famous plunger advance? The placement of the proposed meter window is certainly in the way.

For some time, a Tenax II protoype has been known in which the plunger  advance has been replaced by a horizontal lever that projects from under the frame counter. It was once thought to be a prototype for the military, but with the understanding that a meter window on a Tenax III would require the repositioning of the film advance, this camera becomes evidence of how Zeiss Ikon might have solved the problem of a lever blocking a meter window. This patent drawing also is the first evidence I have seen as to what the Tenax III might have looked like had it been manufactured. While the advance would have had to be relocated, the height of the camera (and therefore, the accessories needed) would have remained the same. The camera would have remained compact and fast operation and ease-of-use would have been unaffected.

The Tenax II prototype. Picture courtesy of S. Baumgartner

The Contax IV itself exists as a several drawings plus a number of incomplete prototypes which Gubas has shared in his book and on line. It was to be a revolutionary rather than an evolutionary product retaining only Heinz Küppenbender's vertical shutter and the external bayonet of the Contax II and III. Why?

The answer lies in patents, corporate politics and the limitations of 1930s technology. The Contax’s vertical shutter was complex and took a lot of space “under-the-hood.” Yet Küppenbender considered it his masterpiece and would not allow its abandonment. What little room was left inside was taken up by the complex internal/external lens mounting system with its built-in focusing mount, gears, sliding focusing prism and the huge bar prism that ran the width of a Contax. To maintain all this, Hubert Nerwin and his design team had to place the meter outside and on top on the Contax III. While a workable solution, it raised the height of the camera and added bulk and weight to a camera already heavier than its Leica competition. It also meant that any finders and other accessories would no longer line up in the same way as ones for the shorter Contax II. This is why there was a separate Contameter  (1340) for the Contax III, as well as different masks for 85 and 135mm lenses.

The Contax IV was an attempt to solve all these problems in one complete redesign. By eliminating the built-in rangefinder system and the internal lens focusing mount, Nerwin was able to gain enough room to move the meter inside the camera, eliminating the meter hump and duplication of accessories. This also meant that all lenses would use the same mount and handle in the same way—a design imperative for Nerwin. The focusing lever and external rotating prism system that the Contax IV advocated was the same as used on the Nettax and had already proved itself on the Super Ikonta series of cameras. It promised the same focusing accuracy as the Contax, but allowed faster focusing via a lever instead of a slow-turning wheel. By continuing the use of the external bayonet mount, all external accessories would remain the same, and legacy lenses would still mount, although focusing would be by guess.

The placement of the meter window below the film advance may seem a bit strange, but it was to be in the camera but away from the rangefinder window. The left hand would now be doing the focusing for all lenses—the same as the Nettax and the Tenax II—and the right hand would remain on top of the camera for winding and shooting. All-in-all, a workable design for both the Contax and the Tenax that would fit into Nerwin’s design priorities for ergonomics and simple, intuitive handling.

The 2.7cm f4.5 Orthometar, Zeiss Ikon's rare wide angle for the Tenax II

The 2.7cm Orthometar lens for the Tenax II. Note that this particular lens is marked in feet. It dates to October 1937, part of a patch of 100 built before the Tenax II camera was released for sale in April 1938.

Hubert Nerwin designed Zeiss Ikon's Tenax II camera of 1937 as a fast-action rangefinder camera with fully interchangeable lenses. That meant its lens offerings had to include at least one wide angle. This proved to be a bit of a challenge. There were few options in wide-angle designs in the 1930s. Initially the Contax had made do with a slow 2.8cm f8 Tessar that did not even couple to the rangefinder. The later fast and sharp 3.5cm f2.8 Biogon was the best wide-angle that any lens manufacturer could offer at that time, but its depth precluded its use on the Tenax. So Nerwin chose  an Orthometar design.
    The Orthometar was designed as an aerial lens by Dr. Robert Richter. As its name implies, it was particularly free of distortion—an important consideration in a lens used for aerial mapping. A modified double Gauss design, it appears similar to the 28mm f3.5 W-Nikkor for the Nikon RF cameras except for a much smaller back element.
    Zeiss also took the design and used it in a 3.5cm f4.5 lens for the Contax cameras—slower than the Biogon, but priced at a lower price point than the Biogon.
   Adapted for use on a 24X24 format camera, such  as the Tenax II, the 27mm focal length yields the same angle of view as a 34mm lens on a 24X36mm camera.

    Although it takes the same 34.5mm screw-in filters as the other lenses for the Tenax, the Orthometar optics are small, a mere 6mm across the front. Grinding the inner elements must have been a difficult and challenging task. The five aperture blades are also tiny. The spaces between aperture markings are even and the aperture closes down to f32. The barrel does not rotate when focused. This is a modern lens lacking only clickstops to make it comparable to any RF lens made today. It focuses down to less than three feet with a 30 degree swing of its under lens focusing lever.

Carl Zeiss made only three lots of this lens: two prototypes in 1937 (nos 2025791 and 2025792), then a production run of 100 finished on October 1st, 1937 (nos.2203301-2203400). A final run of 200  probably came close to a year later (nos 2360001-2360200). The lens was expensive ($132 dollars, or equivalent to over $2200 at 2017 rates) and the market for wide-angles limited. The outbreak of World War II less than a year-and-a-half after the camera’s introduction undoubtedly contributed to the low numbers and small sales.

With such a small production, it is a wonder that this lens is available at all, but I snagged the one illustrated here off ebay with a buy-right-now option complete with its finder and a Tenax camera and custom case. Unfortunately, the camera had been dropped, but with parts on hand I have been able to get everything back in working order.

The lens is easy to use and the results sharp. I like its compactness and easy to set controls.
More details on the Orthometar for the Tenax can be found in my book on the Tenax II, available from Blurb Books:
http://www.blurb.com/b/8032913-the-tenax-ii-zeiss-ikon-s-precision-fast-action-ca

Orthometar mounted on its original Tenax with finder 482/6

Orthometar images

The Tenax II: Zeiss Ikon's Precision Fast-action Camera

I recently put the finishing touches on my book on Zeiss Ikon’s Tenax II camera.

As followers of this blog know, I have been enamored of the Tenax II camera for some time. Having put a great deal of my time into researching the history of the Nikon rangefinder cameras, I decided to branch out a little and investigate one of Zeiss Ikon’s premier cameras in the period immediately before World War II.

I have now published a short book on this unique camera. It is

The Tenax II: Zeiss Ikon’s Precision, Fast-action Camera: A Pictorial Compendium and Gallery of Work.

It is available from Blurb books. Price: $38.49. 104 pages with over 100 full-color illustrations that combine detailed pictures of the camera and its accessories with historic advertisements and my own pictures taken with a Tenax and its lenses.
Go to:

http://www.blurb.com/bookstore/detail/8032913-the-tenax-ii-zeiss-ikon-s-precision-fast-action-ca

The Minion 35: Tokyo's Brave Entry into 35mm Cameras

The Minion 35c camera of 1949

Tokyo Optical Company (Tokyo Kogaku) was founded as a comprehensive optical company with assistance from the Japanese Imperial Army. The aim was to offset the near monopoly on the production of optical glass that until that point had been enjoyed by Nippon Kogaku—founded with the assistance of the Imperial Navy. Like NK, TO grew with many lucrative military contracts only to see that business come to an end with the termination of the war in August 1945.
    It had previously manufactured a 4 X 5cm roll-film camera that it called the Minion III. With the threat of a government ban on all cameras with a format larger than 35mm, the company turned its attention to the smaller format. Like virtually all the 35mm Japanese camera manufacturers that emerged in the mid-occupation period, it was to follow the lead of Chiyota Kogaku and design a camera that took pictures 24 X 32mm. This was the new format that the government was encouraging and which CK (Minolta) was promoting. Other such cameras included the Olympus 35, the Minolta 35 and the Nikon.
 
    The Minion 35 is to be the oddest of the lot. It offered many features that more sophisticated cameras did not, while remaining generally the most primitive of the four. It is small and compact, barely 4.25 inches long. The exterior is finished in brushed chrome and faux leather. The simple optical viewfinder is bright and surprising easy to view through. The Shutter is a Seikosha-Rapid with speeds from 1 to 1/500th of a second plus B. It has substantial strap lugs while many, more-expensive cameras did not. But it has no accessory shoe nor a rangefinder.
    Production first shows up in late September 1948—about the same time as Nikon sales got started. Initial cost was $3.75. (The Nikon with a f2 lens cost $72.00. These cameras were not in the same league.) By December, TK had manufactured 504 Minion 35A and began to work on a new model called the Minion 35B. The principal difference being a body release that linked to the shutter release and sort-of prevented double exposures. Production of both models continued into 1949 with a final count of the 35A at 758. Finally, in April 1949, sales began. That month, TK exported 75 As and 128 Bs plus one Minion 35C.
    The 35C was a new model. It appears to be almost exactly the same as the 35B, but the gearing had been changed to advance film eight sprockets per frame and the picture size was increased to 24 X 34mm—the same size that the Nikon would go to in August 1949. Sales of the 35A and 35B continued, mostly to India and the USA, plus a few to Hong Kong. For the remainder of 1949, sales of all three models coincided even though no more 35A had been manufactured. USA appears to have been the sole export destination by October 1949. By the end of the year, few 35A were being sold and the 35C was accounting for most sales.
    In April, 1950, TK brought out the Topco Reflex (soon renamed the Primo Reflex), its version of a twin-lens reflex and  began to focus all its efforts in that direction. Sales of its little 35mm cameras lingered but by the end of April 1951, none of these camera models were selling.


    So here we have a camera with a removable but mediocre lens in a good shutter. Other oddities are the vertically-striped aluminum front plate that harks back to Art Deco origins, and a circular-shaped pressure plate.
    The camera featured here is a Minion 35C. In shape and layout, it reminds one of a Barnack Leica, and, Leica-like, it loads from the bottom with no way to view the focal plane. Shutter-cocking is separate from the film advance. The lens is a Toko 4cm f3.5 lens. This is a three-element design similar to a Zeiss Novar. Curiously, it is mounted in front of the shutter and can be unscrewed. However, it remains a front-cell focusing lens—which is even more strange. It focuses down to a nice 2.5 feet and is coated—at least internally.
    It has a flash sync terminal on the left corner of the front plate below the lens, but it is not a PC terminal. Since the camera has no flash shoe, a user would have to use an externally-mounted flashgun. The top and bottom chrome plates are finished nicely, but the paint globbed onto the bottom plate’s interior is almost disgusting.
    The shutter front has not aged well, and some of the black paint is gone. Same for the shutter body which has lost nearly a third of its paint. The shutter still fires at all its speeds, but leaves open when being shutter is cocked before closing to its tensioned position. This precludes any picture taking.


   Camera Serial number (112186) is on the bottom plate. That would suggest a manufacturing date of June 1949. The lens number is 111441. The shutter number is 4903878.
    The MIOJ mark appears only on the back of the camera case.

It is always a question for a manufacturer when entering a new field to decide whether to try to get in at the low end or the high end. NK with its Nikon obviously intended to try for the high end. TK even with a background in high-end, military grade products

Bottom-loading like a Leica

opted for the low end. It did well, although not nearly as well as Konica or Canon. But in the end, its equipment never caught on to the same degree as the Nikon.