[dave9t5]

DA used to mean "APS-C" (although some DA lenses have a FF coverage) and FA full frame?

 

Pentax designations are not really clear cut like Nikon with DX/FX designation. 

 

Historically the Pentax lenses versions are:

K was the first K mount bayonet mount.

M was the miniaturized lenses for K mount

A was the auto aperture for KA mount (K mount with aperture connections)

F was the auto focus for KAF mount (KA mount with autofocus)

FA lenses were the last film-era lenses.  They were restyled F basically, but added power zoom for some lenses and a KAF2 mount for powerzoom and transferred MTF lens information to the body.  

DA are digital lenses which technically only indicated that they have digital-optimized coatings and also have NO aperture ring.  (The digital bodies totally dropped stopped down couplers.)  By default, they were APS-C only.

D-FA were digital-era lenses but with aperture rings indicating that they could be used on all older film bodies.  Obviously that requires them to also be cover a larger image circle.  Since Pentax at the time had not FF plans, they were launched as digital lenses that were film compatible.

 

The D-FA designation is the most logical designation for a full frame lens.  (Interesting, these 2 new D-FA zooms are the first in the series to have no aperture rings.)

 

(There were also a couple of other lens series including the FA-J and DA-L which were budget offerings and not worth discussing. Also the Star and Ltd sub-variations are not discussed and which have more to do with build quality than compatibility )

 

Pentax is not always consistent with their naming.  For instance, the two new budget primes in 35 and 50mm should be DA-L lenses, but they are DA.  The current 100mm Macro is built like a Ltd, but it's not designated as such.  The 14mm is built like Star lens but it's not one.  The Ltd's were always primes, then they came out with that stupid variable aperture Ltd zoom which did't make sense on any level.