Why did Leica never implement autofocus in their rangefinders?

Discussion in 'Leica and Rangefinders' started by Colin O, Sep 15, 2019.

  1. My memory from 40+ year old Popular Photography coverage was a bit rusty: when I looked for verification today additional details of Leitz' Correfot experiments emerged. I only remember discussions of the SL2 prototypes back in the '70s, but evidently there were also versions based on the R3 and R4. There also seem to have been two flavors of AF detection: one based in the prism optics above the focus screen, the other mounted at the bottom of the mirror box like in modern cameras. Unconfirmed rumors suggest Nikon may have borrowed the prism-based system for their short-lived F3AF, the last prism-based AF detection design (also the only one to ever be make it out of prototype stage and get sold to ordinary photographers).

    The earlier SL2-AF prototype reportedly used an external minicomputer to process the signals from the detectors. The R4-AF here has the larger customized prism housing ala F3AF. These pics would also suggest an external AC power brick alternative to the huge MOT on-camera battery pack (which seems to have been demo'd most often with the original "manual focus aid" Correfot below, without lens).

    Leica CK2.jpg
    leica af.jpg
    Leica Correfot MF.jpg
    Last edited: Sep 16, 2019
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  2. Anyone who isn't sure about rangefinder focusing shouldn't start with a Leica, unless money is truly no object. Start with a cheaper rangefinder camera to learn if it's comfortable for you. Some old Japanese rangefinder cameras with fixed lenses (i.e., Canon, Konica, Yashica, Olympus) are available for $100 or so. Even an interchangeable-lens Canon rangefinder camera will cost less than a Leica.

    When coupled rangefinders first appeared in the 1920s or 1930s, they were the most advanced focusing technology available at the time. SLRs were still relatively primitive. SLR features such as instant-return mirrors, automatic stop-down irises, and full-aperture metering didn't appear until the 1960s. Until then, rangefinder cameras had the advantage. Today, with autofocus technology, optical rangefinders are largely obsolete. But some people still prefer them. I still like rangefinders and can focus very quickly with them. Others hate rangefinders and love their DSLRs or mirrorless cameras with EVFs. I'm comfortable with all the above.

    The main thing is to get a camera that just feels right. Otherwise you won't use it much.
  3. OP's question implies that Leica owes some kind of justification for their focussing choices. They don't. If you want to really know, why don't you ask Leica? They have a website, and you can contact them.
  4. The autofocus mechanism would have to reside fully in the lens, focus confirmation would have to be feedback from the lens that drives the RF cam in order that the photographer sees the split image align to where they want it. Batteries would have to be contained in the lens, rechargeable lithium polymer would be best.

    Sounds like a Kick-Starter project to me, at a cost of One Million Dollars, stated with pinky to lip.
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  5. Autofocus lenses tend to have little or no damping and a very short throw, 90 degrees or less, and the internals are mostly plastic. AF was mostly unknown when the first M camera was introduced in 1956, and its predecessors were all manual focus too. We bought them because of their relatively simple, rugged construction and small size. I thoght I was doing well with three lenses, 35, 50 and 90. A lot of times, I still prefer manual focus primes for landscapes and just walking about.

    My original M2 served me for 50 years, and is still in good condition except for a flaking "Vulcanite" finish. I bought a used M9 a few years ago. Now that my eyes have been "fixed," cataracts removed, I can actually focus it again, with all the original lenses. Some things just feel good, even if a bit out of date.
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  6. I thought I remembered an early AF system which was pretty much an electronic rangefinder, any maybe (also) Honeywell.

    As I remember it, it would image from the two viewpoints (to make a rangefinder) onto five element photosensor arrays. When the signals on each of the five were close to equal, it was in focus. (Or you were unlucky, and happened to match anyway.)

    When rangefinders work, they work pretty well. I was out with a rangefinder Canon VI a few days ago, after not using it for some time.
  7. Otherwise, not so many years after I bought my Nikon FM, I was looking at the Nikkor 55/2.8, available AI and AF. Not having any intention of buying an AF camera, and liking the feel of the AI much more, I bought the AI. Maybe 25 years later, I got a D70s, which should be able to use the AF version.

    In the 1970's, many point-and-shoot cameras with AF came out, using a variety of methods that sometimes worked.

    That was about the time of the Polaroid SX-70 using an ultrasonic distance finder.
    (Doesn't work through windows.)

    With the FM, I thing I mostly used the center split-image prism part of the finder, and less often the microprism part.

    The nice thing about a rangefinder is that you do know what you are focusing on, unlike AF which might focus
    on the wrong part of the scene.

    For those action photographs (sports, nature) where you don't have time, AF is probably best.

    Most of us, I suspect, use AF when we are lazy. Rangefinders take a little longer.
  8. Nikon brought out a prototype 85mm AF lens ~1970, showed it on a Nikon F. It uses Contrast Detection, much like more modern mirrorless cameras- before PDAF became available on-sensor. The Nikon lens used 6 C-Cell batteries, from memory. I have a write-up on it somewhere.

    I have an F3AF, still works but it;s been a long-time since I put the DX-1 on it.
  9. Short answer, because they make rangefinders. Nowadays Leica make collector's cameras, for people whose income doesn't depend on nailing focus every time.
    As for cellphone cameras, they are just fine for cellphone size photos.
  10. The first version of the Sony/Minolta A to E-mount adapter had a pelicle mirror and motor for AF with SLR lenses. The AF sensors are in the adapter, located below the lens. That would be fairly easy to implement with a Leica M, for SLR lenses from other manufacturers. Power and activation would have be be part of the adapter itself.
  11. In Re: Minolta and Leica AF

    Right, or wrong, my source was Wikipedia

    Minolta - Wikipedia

    the source cited was "Late to Digital, Leica Slow to Refocus", Wall Street Journal, September 16, 2008, p. B1
  12. Theres no "right or wrong" really, at this late date. The archives are too scrambled and confused, Minolta is long gone, and the lawsuit was highly contentious. Leica has about as much interest in its antique Correfot today as my mother, so they haven't published much on it since the '70s. The original version of Correfot was so alien to what became the standard two Honeywell derivations used in 99.9% of film cameras that nobody even realizes anymore that all early attempts at AF weren't the same. The paper trail is too thin.

    The Leica-Minolta partnership proved more fruitful for Minolta than Leica in the long run. All Leica really got was much-needed competitive electronic exposure engineering, which propped up the Leica R system to drag on 20 more years than it would have otherwise, but it still never caught on in a big way and never regained the cachet of the original "Leicaflex" models. OTOH, Minolta gained enormous cred from the connection, made a tidy profit building the CL (a great cooperative idea on paper whose faulty business plan nearly killed Leica), picked up some optical ideas, and key seeds of the AF revolution that would take them to the pinnacle, then subsequently destroy the company.

    Minolta miscalculated the extent of the Leica Correfot patents, and Honeywell was slow to notice at first. The first Correfot, which AF detected like the Nikon F3AF, was discarded in favor of the second. The later Correfot knida-sorta looked like the Honeywell and modern systems superficially, but the AF detection was too complex for mass market SLR camera production. It was a short leap to retrofit the bones of the second Correfot with a more cost-efficient Honeywell-esque detector, so Minolta did just that, to huge success (which unwittingly cut their own throat once Honeywell added 2+2 and got 4). I doubt Minolta was so foolish on purpose: more likely, they sincerely thought their Leica patents encompassed any compatible detection element. They were wrong: its probable this came up in their defense of the lawsuit, but Honeywell was able to shoot it down (without prejudice to Leica).
    Last edited: Sep 19, 2019
  13. All I've ever seen is this schematic. Amazing they showed this as early as 1971, tho one can see why it wasn't pursued: it was enormous for an 80mm lens (as long as a zoom, and heavier at 7.3 lbs with batteries), yet very slow at f/4.5. There was a brief description of how it works in the August 1971 Popular Science, available at this link. And a photo someone took of it at the Nikon Museum opening can be found here.

    Last edited: Sep 19, 2019
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  14. I suppose so, but I always thought at the Kodak Instant Camera vs. Polaroid patents were a more obvious mistake. Then again, the Kodak version never got all that popular.
  15. You mentioned your cell phone, so I'm assuming you're not tied to film, correct? Without over thinking and analyzing this I'd recommend one of the following, based on MY experience. I wanted to see if I wanted to invest in a Leica rangefinder camera but was into digital so bought a Fuji X100T and it's been a fantastic travel autofocus rangefinder with outstanding image quality. That camera led me to purchase an M2 with 50mm Summicron lens and I much prefer that over the Fuji. Sure, I miss some shots but it's the experience of carrying and using that camera that is magic, like a bamboo fly rod, a fine side by side double gun for bird hunting, or a fine crystal glass to have your single malt in. It's the experience. So the first suggestion is a camera like the X100T. Just got back from a fishing trip and carrying my D850 tucked into my waders will not work, so I got an Olympus OMD5MkII, a mirrorless with 50-300 lens effectively. Small, unobtrusive, and outside some very poorly designed menu layouts (I shoot RAW and aperture priority only) I find this camera to be versatile and just my most used camera now. I got great landscapes out west, great candid and family shots, then shot about 750 frames at my sons soccer game on high speed shutter with the 300. Incredible at about 1/6 the price of a newer Leica. I own more cameras than I can use, but of my smaller cameras outside my 4x5 and Hassy, the M2 and the Olympus get the most use for ease of use and carrying. YOU WILL USE WHAT YOU CARRY MOST. If I was held at gunpoint to choose one, while the Leica is my favorite by a long shot, the Olympus is much more the practical camera doing much more and I can get more shots with it, so I'd choose that.
  16. As long as the ambient lighting allows, setting a RF (or any other manually focused) lens to the appropriate hyperfocal distance for the aperture used, negates the need for autofocus; there’s zero focusing delay, no missed “decisive moments.”
  17. Remember . . . DOF allows for "acceptable focus" . . . there is still only one distance at which focus is correct. I'm not saying that hyperfocal focusing is of no use but is it still a compromise.
  18. If you include diffraction, there is no distance at which focus is correct, only where it is closer than other distances.

    Around that point, there is very little change, so a DOF seems reasonable.

    Next there is film or sensor resolution, which adds to the focus uncertainty.

    But yes, usual DOF calculations assume a reasonable circle of confusion for
    ordinary image viewing at ordinary distances.
  19. Funny, I always had trouble nailing focus with my Canon 7D AF system. I hardly ever miss the focus point I intend with my Leica.
  20. As I understand it, the reason Leica never incorporated autofocus into their M cameras is due to the M camera ethos. Part of that ethos is that the M camera will retain the physical dimensions of the original M camera footprint. At present, there is precious little room to cram more stuff into the M camera dimensions, and an autofocus mechanism takes up a lot more space than is available in the M camera.

    The M240 was .20 of an inch thicker than the traditional M camera and M camera users raised 99 kinds of hell. Leica took the hint and returned to the original M camera size specs in the M10. That involved using a smaller battery in the M10 which had a significantly shorter power life before needing to be recharged than the M240 battery, but it was a sacrifice that the gents in Wetzlar were willing to make and M10 buyers were willing to live with.

    As far as missing shots due to the absence of autofocus in M cameras, anticipating the decisive moment goes a long way in circumventing that. Autofocus is a two edged sword. It helps in some situations, but is next to useless in low light shooting. AF also struggles with low contrast and subjects with little to no texture. At the end of the day, it's a tradeoff.

    Personally speaking, I am actually glad my M-P 240 is manual focus. The number of images I miss in low light shooting is drastically reduced thanks to manual focusing.

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