I was curious, so had a look at the Pentax web site to compare the K-3/K-3 II AF system [SAFOX 11] with the K-1 AF system [SAFOX 12].
It was interesting to see that the K-1 appears to share exactly the same AF and metering chips as the K-3/K-3II. (I guess this technology re-use is one factor in keeping the K-1 affordable).
However there are some notable differences between SAFOX 11 and SAFOX 12, as one can see from the infographic I put together below.
From the
K-1 AF features page, Pentax expains the new SAFOX 12 features:
Quote: The K-1’s AF frame has been widened to optimize the ease of image composition over a larger 35mm full-frame image field. Thanks to the development of a new SAFOX 12 AF sensor module, its autofocus area is approximately 40 percent wider than a conventional AF frame.* In order to contain a longer optical path required for the expanded AF area within a compact housing, the K-1 features an innovative, efficient optical design in which the incoming light is turned back within the AF module. Thanks to the optimization of the condenser lens, it also provides an increased number of AF sensor points (33 in total)...This new AF sensor module features two reflex mirrors. By reflecting the incoming light flux twice on these mirrors, it provides a longer optical path, while its overall size has been kept nearly identical to that of SAFOX 11.
Cleverly, the extra AF points in SAFOX 12 come about as a result of changing the condenser lens in the AF module, not from using a new chip.
Aside from the design changes mentioned above, SAFOX 12 now seems to lack the diffractive lens present in SAFOX 11 AF module, which is interesting. This lens was there to improve AF precision by correcting CA in the AF unit. Not sure of the impact of this.
But whilst the SAFOX 12 module has lost this diffractive lens, it now seems to have gained an IR cut-off filter, placed directly in front of the AF chip, which SAFOX 11 didn't seem to have.
Also notable is how 'color motion detection' in the K-3/K-3 II has changed to 'shape detection' in the K-1 in the Pentax 'Real-time Scene Analysis System', which:
Quote: "analyzes such factors as brightness distribution in the image field, the subject’s primary color and its motion with great accuracy and efficiency. In addition, by adopting a breakthrough artificial intelligence technology called deep learning to its image detection algorithm*, this system assesses each individual scene more accurately, while optimizing the accuracy and performance of the light-metering, exposure-control and autofocus systems ...".
However this 'deep learning' intelligence in SAFOX 12 unfortunately only seems to help the AF if the K-1 exposure mode is set to 'Auto' (not Av, P, TAv etc). In contrast, SAFOX 11 was able to benefit from 'color motion detection' in any exposure mode.
There may be other algorithmic and software changes in the K-1 compared to the K-3/K-3II (eg AF-C settings and other AF customizations), but the web site doesn't document these features very well, and the K-1 manual doesn't appear to be available yet.