[Dlanor Sekao]

The FA 20 (and its A20 optical twin) are retrofocus designs, so they should be fine on FF digital.
(Maybe some Canon FF user can give us their actual experience here.)

Also, if you look at the MTF charts I posted on my recent review of the A20
(SMC Pentax-A 20mm F2.8 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database),
you will see that there is actually some improvement of performance
as you move out to FF from the corners of the APS-C frame.

So are you saying The FA is the exact same as the A as far as the optical elements ? If it is I have ZERO problems with manual A lenses and will jump on it. I just don't need autofocus at all for my shooting. I see it is one expensive lens also , but not quite as much . Also noticed the 20/4 SMCK is even higher rated

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Last edited by Dlanor Sekao; 08-27-2013 at 10:18 AM.

[lytrytyr]

So are you saying The FA is the exact same as the A as far as the optical elements?

Yes, that is my understanding.
It seems to be confirmed by the shared listing in Boz Dimitrov's authoritative site:

Pentax Ultra-Wide Prime Lenses

and on the local site:

SMC Pentax-A 20mm F2.8 Reviews - A Prime Lenses - Pentax Lens Reviews & Lens Database

That said, the coatings on the FA 20 may have been improved.

While the replacement of "SMC" by "HD" on the DA Limiteds
is something of a recent exception,
coatings were steadily improved over the years
without any announcement.

Anyway, if you don't need AF, you'll save some money going for the A20/2.8,
although it can be hard to find.

KEH does have an "ugly" one for $265,
which may be perfectly usable.

[Dlanor Sekao]

Thanks lytrytyr ! I found Dimitiov's info page very helpful and informative. Not only on this lens , but also on another one too. I was pondering the 24mm SMC"K" , but see it is the same as the "A" version except for possible better coatings on the "A"........yet another thing to consider.
Im right in the middle of "Going Digital" all the way at this late date , and Im almost overwhelmed getting it all together. Its kind of a frazzled muddled mess in my mind right now , but slowly coming together in the next couple weeks. Thanks to everyone.