these charts might help folks:
Pentax Lens Compatibility Chart
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Pentax bayonet lenses labeled "SMC Pentax" are referred to as "K" lenses in the table below. Other Pentax bayonet lenses have the lens designation as a part of their name as in "SMC Pentax-FA".
Note that "star" lenses work like their "non-star" counterparts unless they are singled out in the table below. So for compatibility of a DA* lens, look under DA lenses, etc.
Exceptions: FA and F "soft" lenses behave like M lenses in terms of metering.
The Pentax Camera Lens Compatibility Chart
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Pentax K-Mount Lens Series Explained: The differences between various Pentax lens series
In a nutshell
There are several series of Pentax K-mount lenses; the ones currently being produced include the DA (digital), DA L (cheap digital kit), D FA (full-frame, digital optimized), and FA (full-frame) series. While all Pentax K-mount lenses ever produced are compatible with all current Pentax DSLRs (in some cases with restrictions in that not all exposure modes of the camera are supported by old lenses), there are significant differences between each lens series and each has different features. Furthermore some of the newer lenses do not work with older cameras. We'll be exploring the differences between the various K-mount series lenses in this article. Read more about specific K-mount lens/camera compatibility here.
The DLSR designation below encompasses the mirror-less K-01.
Pentax K-Mount Lenses Explained: The differences between various Pentax lens series
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and of course, the early Pentax lenses used a screw mount, not a bayonet mount :
The M42 lens mount is a screw thread mounting standard for attaching lenses to 35 mm cameras, primarily single-lens reflex models. It is more accurately known as the M42 × 1 mm standard, which means that it is a metric screw thread of 42 mm diameter and 1 mm thread pitch. (The M42 lens mount should not be confused with the T-mount, which shares the 42mm throat diameter, but differs by having a 0.75mm thread pitch.) It was first used in Zeiss' Contax S of 1949; this East German branch of Zeiss also sold cameras under the Pentacon name; after merger with other East German photographic manufacturers, the name Praktica was used. M42 thread mount cameras first became well known under the Praktica brand, and thus the M42 mount is known as the Praktica thread mount.[1] Since there were no proprietary elements to the M42 mount, many other manufacturers used it; this has led to it being called the Universal thread mount or Universal screw mount by many. T
he M42 mount was popularized in the United States by Pentax; thus, it is also known as the Pentax thread mount, despite the fact that Pentax did not originate it. M42 lens mount - Wikipedia
an adapter is needed to use the screw mount lenses on modern Pentax lenses:
https://www.pentaxforums.com/accessoryreviews/pentax-mount-adapter-k.html