ok
exposing some of my great lack of knowledge
FA limited lens:
SMC Pentax-FA 31mm F1.8 AL Limited
SMC Pentax-FA 43mm F1.9 Limited
SMC Pentax-FA 77mm F1.8 Limited
DA limited lens:
old - SMC and new - HD relating to the coatings applied to the optical glass
Pentax-DA 15mm F4 ED AL Limited
Pentax-DA 21mm F3.2 Limited
Pentax-DA 35mm F2.8 Limited Macro
Pentax-DA 40mm F2.8 Limited
Pentax-DA 70mm F2.4 Limited
( I know that because " Limited " is in the name )
and FA means full frame while DA means not full frame ( at least officially )
and " limited " appears not to mean limited as to quality but rather physical size, they are small good or better quality and metal throughout and have quick-shift focusing, allowing you to override the autofocus mechanism at any time, and it also has a proper distance scale.
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the closest I have to any is my DA 40mm 2.8 XS which is entirely plastic except for the metallic mount
what if anything am I missing ???
is there something special about the optics of the limited series as well as compared to other Pentax lenses of the same focal length
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FYI since I first posted this, I added to my lens collection and now I own a smc Pentax-DA 21mm F3.2 Limited that I purchased from a member through the forum's market place
I like it a lot https://www.pentaxforums.com/lensreviews/SMC-Pentax-DA-21mm-F3.2-Limited-Lens.html