Thursday, November 21, 2013


Leica is often criticized for not offering autofocus for the Leica M.  Many feel that this is really the final step necessary to make the M fully competitive with the top models from other manufacturers.

Yet it is a actually a little known fact that Ernst Leitz Wetzlar GmbH (the name Leica Camera used to be called) was the first company to develop a working autofocus system.  Between 1960 and 1973 the company patented a number of autofocus technologies, and then showed that technology at the Photokina in 1976 and 1978 as the Leitz Correfot.  A further improved prototype was shown to the public at the Leica Historical Society of America (LHSA) meeting in Minneapolis in Fall of 1980.

The common CdS light meter cells at that time proved to display also a sensitivity to variations in contrast.  It is a known fact that an image displays the highest contrast when in focus.  By using two CdS cells it was possible to accurately determine the highest contrast level and thus accurate focus.  The system was somewhat similar in concept to today's phase-detection systems - except that it required a vibrating diffraction grating to work accurately.

The prototype was a completely operational system built into the shell of a Leicaflex SL2, renamed CK2.  All sensors necessary for the automatic focusing were part of the camera.  It was designed to use the conventional Leica R lenses on the market at that time.  The system required the lenses to be focused manually with the help of focus verification via two LEDs on top of the viewfinder.  But like the camera shown at the LHSA meeting in Minneapolis, the Leicaflex SL2 was also shown with a servo motor equipped 50mm f/1.4 Summilux R which provided true autofocus operation and made electronics-aided hand focusing unnecessary.

The servo motor was connected to the lens via a gear that engaged with the ridges engraved in the focusing ring of the lens.  With other words, it actually turned the conventional focusing ring to effect automatic focusing.  Leica chose this approach at the time because they felt it was necessary to utilize their very precise focusing mounts to maintain the mechanical and optical integrity of their lenses.

At that time it was generally thought that autofocus systems suffered from low-light insensitivity.  However, I personally was able to verify that the system worked perfectly in even very low light conditions and no manual refocusing was necessary at all.  However, the camera did display one serious drawback, very high power consumption.  The prototype’s servo motor used lots of energy which was supplied by a battery pack attached to the bottom of the camera.  It was made from the housing of a Leica R3 motor drive unit.  The six batteries proved to be good for only one hour of operation.

Careful inspection of the lens revealed meter couplings for the Leica R3 and R4 cameras.  These were utilized in a follow up model, based on the Leica R4 Mot prototype with special Correfot prism.  

In 1983 Nikon presented an evolution of its flagship camera, the Nikon F3AF with its viewfinder DX1 and its two lenses, AF 80mm f2.8 and AF 200mm f3.5 ED.  Although never officially confirmed, it is said that Nikon purchased the manufacturing rights for the Correfot prism from Leitz  to develop the F3 AF.  

The Leica R4 Mot prototype was replaced by the R4 Mot CK3 for which Leica also produced an auto-focus prototype lens Summilux 1.4/50mm

We must applaud Leitz’ decision not to forego their standard focusing mount for the flimsy autofocus systems that were marketed in the 80s and 90s.  Virtually without exception, those were so loose that the moving section of any of those lenses could easily be wiggled back and force by a considerable margin.  That of course is far removed from the 1/100mm (1/2500 inch) precision of the Leica focusing mounts.  Other companies chose that approach because it was the only means at the time to make the focusing parts of their lenses move easily enough to allow the use of rather small autofocus motors with low enough power consumption to make them practical with common use.

Unfortunately Leica never marketed their autofocus cameras thus missing out on having been the first company to do so.  That honor goes to Minolta, who introduced the Minolta 7000 in 1980. 

At that time Leica had a technology exchange agreement with Minolta.  The Minolta 7000 would have never seen the light of day without the Leitz Correfoot technology.

Although it never made it into production, it appears that the Correfot serves its duty in the German Leopard tanks to this day.


  1. I wonder what Leica would be like today if they had marketed their autofocus system in a camera of their own. Did they ever say why they didn't?

    1. Of course we will never know. However, I do think that the Leica R cameras might have been more successful.
      Leica never made any official statements about why they chose not to use the Correfot system. The general assumption is that they thought it wasn't necessary, that their customer didn't need or want it because they were well able to focus their Leicas themselves.
      Unfortunately it is this 'we know best' approach that brought Leica to the brink of bankruptcy and which lead to the demise of many German camera manufacturers. Rollei is a good example. They held on to the twin lens reflex cameras much too long. Then, when they finally changed their minds, they had lost so much market position that they never recovered and finally faded away.

    2. Two questions; Isn't there some Rollei equipment marketed? And what medium format cameras did Rollei make after their TLRs?

    3. Yes, there is some Rollei branded equipment available in Europe and Japan, but that has nothing to do with the old Rollei company. Several years ago Rollei was taken over by a new company and was renamed from their original company name of Franke and Heideke to Rollei Fototechnik. They went out of business a short while ago and sold the naming rights to a Japanese company who now is marketing equipment from a variety of manufacturers under the Rollei label. After the demise of Rollei Fototechnik, the sons of company founders Franke and Heideke resurrected the old company name in a new venture. They started manufacturing the Rolleiflex TLR cameras again, including the Rollei Wide and the Tele Rollei. In addition they also made the Rollei 6008 which evolved to the Rollei Hy6. The same camera was also marketed by Sinar as the Sinar Hy6.

      As for your second question, long after it had become obvious that medium format SLR cameras were the wave of the future, Rollei finally introduced the SL66 medium Format SLR camera. At that time Hasselblad was the market leader. Even though the SL66 was superior to the Hasselblad, it never made any sizable inroads into that market. A few years later Rollei added their first electronic camera to the line up, the SLX with its built-in motor. This camera soon evolved via the 6002 and 6006 to the 6008 and later the digital, autofocus version, called Hy6. All of these were remarkable cameras, as good as anything on the market. But most professional; photographers went with cameras from the competition and a couple of years ago Rolle, or Franke and Heideke,i closed its doors forever.
      Please note that I commented strictly by memory and that some mistakes might have been made.

    4. Thanks for the extensive reply. If you don't mind another question, what made the Rolleiflex SL66 superior to the Hasselblad?

    5. One of the reasons for the outstanding performance of the Hasselblad were the Zeiss lenses. The Rolleiflex SL66 was equipped with the same lenses. But unlike the Hasselblad, which only offered lenses with leaf shutters, the SL66 had a focal plane shutter. This eliminated the necessity of every lens needing a shutter and the SL66 lenses were a bit less expensive. In addition, the 80mm f/2.8 Planar and the 150mm f/4 Sonnar were available with leaf shutters for faster flash such speeds. The main advantages of the SL66 were the features of the camera body. The camera featured a bellows which allowed instant close-up capabilities without any accessories at all. In addition, the camera also had a built-in lens reverser which allowed reproduction ratios down to 1:1, at no extra cost because no additional accessories were needed. The bellows also could be tilted up or down, or with the camera mounted on its side, tilts right and left. This allowed for the Scheimpflug principle to be applied for greatly extended depth of field. The tilt feature could also be used for the correction of converging lines in architectural photography. Unlike the Hasselblad, where an additional magazine was needed for the use of 220 film, the Rollei film backs could be switched from 120 to 220. Another advantage of the SL66 was its top shutter speed of 1/1000 sec. Finally, the SL66 offered a wider range of lenses. On the Hasselblad, the 500mm Tele Tessar was the longest lens. This was available on the SL66 as well, but in addition it also offered the 500mm f4 Zeiss Mirotar and the 1000mm f/5.6 Zeiss Mirotar which were unusually fast at the time for lenses of this long a focal length. While the Haselbald could do double exposures, this was quite cumbersome. After the first exposure, the film back needed to be taken off the camera. The the camera could then be cocked and after the back was re-installed, the additional exposure could be made. The SL66 offered double exposure via a simple push button which deactivated the film advance and only cocked the shutter. Of course the camera had interchangeable focusing screens and interchangeable viewfinders.

    6. What is the Scheimpflug principle? Also, Hasselblad claimed that two different backs were needed to accommodate 120 and 220 film more accurately in terms of film flatness and focusing accuracy.

    7. The Scheimpflug principle refers to tilting the lens up or down or from side to side (swing) to effectively tilt the plane of focus, thus gaining a considerable apparent gain in depth of field.

      Hasselblad refers to the fact that 220 film does not have the paper backing of 120 film. The paper leader and trailer are glued to the film instead of the backing covering the entire length of film. Thus there is slight difference in the film position relative to the lens. This is compensated for in the Hasselblad 120 and 220 backs. The Rollei approach makes the same changes, however with one and he same camera back when switching from 120 to 220 film. There too both the film gate and the pressure plate are repositioned as necessary.

  2. Why all this talk about Rollei and Hasselblad? I thought this was a Leica Blog.

  3. Of course this is a Leica blog, but we don't operate in a vacuum. If a reader asks a valid question, I will answer it.

    1. I agree. Some Leica owners are too full of themselves and come across as snobs because of it. There is nothing wrong with discussing other cameras if the opportunity arises.
      Here is a question about the Correfot: Is the Correfot system still in use in cameras today?

    2. The Correfot system utilized the contrast sensitivity of CDS (Cadmium Sulfide) cells. They were the metering cells used by most light meters, hand-held or built-in. Since then things have changed considerably. CDS cells are not in use anymore. For autofocus systems they have been replaced mostly by infrared sensors to effect the automatic focusing of lenses.