this may be redundant if so, sorry:
[ please note that the info below fails to account for "XS" which is a designation class with only has one lens as far as I know:
the SMC Pentax-DA 40mm F2.8 XS
https://www.pentaxforums.com/lensreviews/da-xs-prime-lenses-c68.html ]
info on initials ( designations ) used by Pentax:
3. Terms to Know
AW or WR? DC or SDM? Here’s how to decode Pentax lens names.
If you’re in the market for a new Pentax lens, you’re going to be wading through an alphabet soup of acronyms and unfamiliar terms as you shop. Here’s what you ought to look out for.
Pentax Lens Detail
DA: This is the basic label applied to Pentax lenses designed to cover the APS-C image sensor.
DA L: DA L lenses are lightweight, less expensive versions of existing Pentax DA lenses, often sold bundled with the company’s most affordable DSLRs.
FA: This is the basic label applied to Pentax lenses designed to cover the 35mm full-frame image circle.
D FA: Describes full-frame lenses designed in the digital era.
★: DA* and D FA* lenses feature robust build quality, high-quality optics, and weather sealing, making them suitable for professional use.
Limited: DA and FA Limited lenses feature all-metal build quality, unique focal lengths, and compact design.
Pentax WR Weather Sealing
Pentax WR lenses include a visible red o-ring seal around the lens mount, along with various internal seals that you can't see.
DC: Short for “direct current.” Refers to Pentax’s newest kind of electronic autofocus motor.
SDM: Short for “Supersonic Drive Motor.” A type of electronic autofocus motor that was used in some DA* lenses.
WR: Indicates that a lens is weather resistant—sealed against moisture and dust. WR lenses feature a bright red o-ring gasket on the metal mount.
AW: A beefed-up kind of weather sealing found on some DA and D FA* lenses. DA* lenses feature weather sealing generally considered equivalent to AW.
AL: Describes lenses that use aspherical elements, which help produce higher corner sharpness and reduce optical aberrations.
ED: Describes lenses that employ extra-low dispersion glass elements, which can help eliminate chromatic aberrations (color fringing) in photographs.
SMC: Short for “Super Multi Coating,” this was Pentax’s standard lens coating for many decades. Designed to reduce flare, ghosting, and internal reflections.
HD: This is the new Pentax lens coating, which the company says provides a more than 50% reduction in reflections over the previous SMC coating. May also reduce flare and ghosting.
RE: Describes collapsible lenses, which are designed to be more compact when not in use.
A Guide to the Best Pentax Camera Lenses - Reviewed.com Lenses
A Guide to the Best Pentax Camera Lenses - Reviewed.com Lenses
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---------- Post added 07-31-17 at 09:41 ----------
Originally posted by Sandy Hancock The SMC Pentax-D FA 1:2.8 100mm macro WR is as good a lens of its type that you will find from any manufacturer. It is beautifully built and quite compact. It focusses close enough for true 1:1 magnification and is very sharp across the frame from f/2.8. It also works very nicely as a portrait or landscape lens.
D FA refers to it being designed for the full 36x24 frame, and also for the digital era. So no worries whatever you choose. I use mine on both crop and full frame bodies. . . .
If cost is a factor, you may want to consider the 100 macro which is what I have
as I understand it, the optical components of both the 100 macro and the 100 macro WR are the same
that is not to say that there isn't differences between the two, there are but - - -
the newest PLM does have different optical components