Originally posted by pres589 The one lens that the K-5's cannot drive, the 55-300 PLM RE WR seems like a nice lens. There's piles of 55-300's that it can deal with, the older version, that isn't much behind the Retractable in image quality. There will probably be more issues like this in the future, but when? And which lenses? It seems really minor when we're talking about someone just dipping their toes into Pentax DLSR's.
perhaps this information can be of help
these articles explain how the various Pentax Camera bodies work with the various Pentax lenses and have info on the types of Pentax lenses
"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: DA* lenses work like DA lenses, FA* like FA, F* like F, A* like A, and M* like M.
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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" The Evolution of the Pentax K-mount
Technical Information and a Little Bit of History "
Read more at:
https://www.pentaxforums.com/articles/photo-articles/evolution-of-pentax-k-m...#ixzz5HBMlIs3h