[chickenandavocado]

With the new FF, I now want something in the equivalent 22mm range to replace my DA15 to take advantage of FF, with the hope of having.

Any FF lens suggestions that are small and compact? At the moment I'm looking at the Fa20 but would like to know of any more compact alternatives.

Autofocus is not a priority for me, but rather compactness and sharpness stopped down

[JinDesu]

The Sigma 24 2.8 comes to mind.

[dunerunner]

The M20mm sounds like a good fit for you, it is nice and small. Check out the Pentax Lenses on FF thread on the last few pages. Lots of examples. I have a K20mm, it is somewhat larger and harder to find. https://www.pentaxforums.com/forums/122-lens-clubs/247282-pentax-lenses-ff-club.html

[AquaDome]

The Sigma Super-Wide 24mm/2.8 and the Ultra-Wide 18mm/2.8 are both available with A setting. They're no bigger than a regular M50/2.

[zzeitg]

I have FA20 and can only recommend it. I guess FA*24 must be very good lens, too.

[lytrytyr]

Any FF lens suggestions that are small and compact? At the moment I'm looking at the Fa20 but would like to know of any more compact alternatives.

There are two manual focus pancakes:
the M20/4 as mentioned above,
and the Cosina/Voigtlaender Color Skopar 20/3.5.

The good news:
both have very nice color rendition.

The bad news:
both will vignette unless stopped down,
both have mustache-style distortion,
which is not that easy to correct,
and both have weak edges on FF,
worse than the DA 15 on APS-C.

[Biro]

Sigma also has a 20mm f/1.8 that's pretty good. Quite a bit larger than the DA 15mm Limited, though. Still, it is faster.

20mm F1.8 EX DG ASP RF | Sigma Corporation of America

I'm only mentioning this for the record as the OP sounds like he really wants something compact.

[DSims]

The A24/2.8 is nice, in addition to the FA*24 and FA or A20. Since you're stopping down the A24 makes sense.

[carpents]

I would echo the A24/2.8.

[lytrytyr]

I do have A and K versions of the 24/2.8.

Their edge resolution on 16MP APS-C
is already at best only marginally acceptable,
so I wouldn't expect miracles from them
on a modern FF digital sensor.

Several users have tried them on Sony A7 cameras,
and their reports have not been enthusiastic.

E.g: "produces good images albeit somewhat soft at the edges".

https://www.pentaxforums.com/reviews/sony-a7-with-pentax-full-frame-lenses/pe...rformance.html

[Rondec]

The problem is that what is best about DA 15 mm limited (its flare resistance) is unlikely to be true of most full frame lenses. The more glass you have, the more likely you are to get flare and internal reflections.

Otherwise, I think there are a bunch of 20mm-ish lenses that are plenty sharp and have good contrast on full frame.

[hoopsontoast]

The Sigma 24mm Super Wide II in AF is a gem of a lens, IF you can find one.

Sigma 24mm F2.8 AF Super Wide II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Other than that I guess its really only the Voigtlander 20mm/f3.5 and the K/M/A/FA 20mm or 24mm variants mentioned as far as I can see. The FA20-35 is a personal favourite on 35mm film, but thats a larger (still compact) and lightweight zoom and smaller than the Sigma 20mm f1.8 mentioned.

[jimr-pdx]

My SMC 17/4 fish-eye has great color and contrast & is at home on film and digital. Small, close focus.. and just a bit bent . On sale in the marketplace as we speak though, paying off a few other optical wonders.. bummer.

[carpents]

I do have A and K versions of the 24/2.8.

Their edge resolution on 16MP APS-C
is already at best only marginally acceptable,
so I wouldn't expect miracles from them
on a modern FF digital sensor.

Several users have tried them on Sony A7 cameras,
and their reports have not been enthusiastic.

E.g: "produces good images albeit somewhat soft at the edges".

Sony A7 with Pentax Full-frame Glass Review - Performance / Handling of Pentax K-mount Lenses | PentaxForums.com Reviews

But is that a function of the A7 or the lens? Could be either, or a bit of both.

[Na Horuk]

The DA 15mm is so special, I don't think there is any FF equivalent. But you can find some lenses of similar FoV. When I read the thread title, I thought of the Voigtlander and Zeiss primes