The Pentax autofocus system: patents and development. The Safox III myth.
SAFOX, or more correct SAFOCS means in official Pentax language: Sensor Ability Fortifying Optical Compensation System. This of course is only another marketing language excess for an ordinary phase comparison principle autofocus system. It derived from the late 80's when such tech slang was very much in fashion. Pentax created more such horrible terms, like CENTIC for the prism cap located LCD-monitor or PROCES for an integrated metering system with automatic backlight compensation. Pentax stayed with the term SAFOX for their autofocus system also in the (P)Z-series and the MZ/ZX-series. (P)Z-series had SAFOX II, clear, since this was Pentax second AF-camera system (I skip ME-F here, but I will mention it later). For the rest of the world this was the so called third generation autofocus systems, because from early 90's on predictive AF with good light sensitivity and fast reaction times were the new standard. Due to Pentax's late start in AF this was now SAFOX-II. It was updated several times in terms of software logic and motor speed, but the sensor itself stayed the same, and so did the name.
With MZ/ZX-5 in the mid 90's the number of detection fields were increased to three. At Pentax the detectors are still in one line on the sensor chip, so in principle it's still a pure vertical pattern detector. But a clever mini-prism and mirror arrangement in front of the sensor changes the orientation of the outer fields for horizontal detection, forming a "H" with the middle sensor. With another front optics arrangement, one can form also a "+" or a "x" or a "-I-", there is a lot of room. Unfortunately they didn't use the "+" option on the cameras without AF-spot switch, but that's another story. This AF-system is called SAFOX IV. Yes IV. there is no SAFOX III. Either it was a cross sensor prototype that was shelved (technical problems? Patent situation?) or it was the passive 5-beam AF-system that was developed for the zoomcompacts in 1994. Anyway. The new MZ/ZX-50 has now a system SAFOX V, again with a single sensor area, so this is very similar to SAFOX II, but for marketing reasons Pentax wanted a new name.
How was the name SAFOX invented? Officially there is the version that there was the new SAFOX-system, and therefore the according first AF-camera series was called SF. Like SaFocs (another possibility would have been SOCS...). Now, sensor ability fortifying and so on is a very complicated way to describe a modern AF-system. So I believe this is all nonsense. I think, the SF-series had a kind of working name during development. This was combined from the first Pentax AF-camera ME-F and the mid-line top model Super-A/Program. So it was called Super-F. SF. And later a poor guy in the marketing department had the job to create a name for an AF-system including these letters. Not only SF (sensor fortifying is o.k. in principle), but also the X, because in international market the first SF-camera was named SF-X (from KX, MX, LX and so on). X... o.k., compensation system! but "SSFFXX" is different to spell - lets include some vocals. Optical. Ability. Ability. Optical. And so on.
Note by the author: maybe this is all wrong and they are really so crazy to call a simple AF-system "sensor ability fortifying" ... which reminds me a little bit at terms like "taste enhanced"...
By Ralf Engelmann
A classical question in Pentax AF history is why the version numbers of the AF systems jumped from SAFOX II in the (P)Z-series to SAFOX IV in the MZ/ZX-series. So far no one had a real explanation for this nomenclature, but some rumors were around: 1st, SAFOX III could be a silent update in software logic speeding up SAFOX II speed in (P)Z-1P and (P)Z-70 cameras, but since the sensor stayed the same, Pentax didn't change the official designation. Or, 2nd, SAFOX III was the passive 5-point AF system designed for the 1994 zoomcompacts, but also not mentioned officially. Or, even, 3rd, the whole thing was simply a marketing trick; the jump from II to IV should indicate how new the MZ/ZX-5s AF-system was.
A look at the AF-technology patents hold by Pentax gives another explanation. If SAFOX III exists, it should be dated after 1991 and before 1995. It is very much surprising to see that Pentax has several patents on hyper modern AF-technologies deriving from this time. Most of them were not realized in the known cameras, so these patents can be considered to be the mythical SAFOX III.
What is the technology described in these patents? Well, a big surprise. Pentax was amongst the first to develop a three field eye controlled cross sensor AF-system. The first patents deal more with the three field AF, then the eye control came in and later the eye control was improved.
The latest patents deal with the question how to miniaturize such a system to work in cameras with small bodies. So Pentax was not only amongst the first doing research in this field, they also constantly developed it further.
One might speculate now why such a system was not included in (P)Z-1P's update in 1994. At least the three field AF should have been functional. Maybe they thought about the whole thing only in terms of a complete system, and since eye control wasn't ready, they didn't include it in (P)Z-1P. Later then MZ/ZX-series happened, so again development efforts were necessary to make the whole system smaller. Or they shelved the whole idea, since a three field eye control system was meanwhile a technology for middle class cameras like Canons EOS 50/Elan II, whereas the new pro cameras suddenly had no eye control anymore, but a 5-field AF-systems with a thumb selector. The story itself makes the MZ/ZX-1 saga of course even more interesting, since the big question is now: Was (P)Z-1P only an intermediate in the constant development of an SAFOX III camera, becoming necessary because of development delays? Or is the whole thing a matter of history meanwhile, and Pentax only holds the patents to tease Canon and to hinder them to make smaller cameras with eye control?
By the way, the delay between development and patent is two years or more, so we still have no insights what Pentax or the other companies are doing at the moment. On the other side, it's also a long way from developing a prototype to a serial product. So the patents can give some hints, but not a clear image what will happen in the camera industry in future.
Note by the author: Of course all the developers and product managers know the patents of the other companies very well, since patents are open for insight and most of the patents have been available in Japan much earlier than internationally. Also patents are very much a tactical thing, so sometimes important techniques have no patents, because the thing is so new that the other companies have to invest several years of research to catch up anyway, and sometimes less important things have patents, since companies want to hinder others to do it a similar way.
The original articles were published on SPOTMATIC magazine #15, January 1998.
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