Need K-01 lens advice

It's absurd that Pentax has so many primes, and none with the traditional 35mm equivalent FOV.

You should have a look at legacy glass. There is a FA*24mm f2 that is no longer in production. It sells for the cost of a new lens, when you can find one, and it's large compared to some other possible choices. There is no auto-focus 24mm f2.8 in Pentax, but there are several 24mm A lenses which have electronic aperture and manual focus. Not so bad with focus peaking. Sigma has a 24mm 1.8, again kind of large. It may be worth a look, although given a choice I prefer Pentax lenses.

The DA 21mm Ltd as others have mentioned, is small and speed is sufficient for most uses. I tried one and didn't much like the focal length for general use. I am very touchy about shooting people with wide angle lenses because if they're too close to the lens, you get the "big head, little body" effect.

I favour normals over wide angle for general purpose; no wide-angle stretching and still wide enough for indoor use. For K-mount, the most normal focal length is 28mm. The obsolete F 28mm 2.8 has a good reputation, and can usually can be found for around $275. I bought an FA 28mm f2.8 in excellent condition for $240. Both are compact lenses with good IQ and auto-focus. I also have an FA 35mm f2 which I believe can still be found new. I usually prefer to carry the 28mm for its wider FOV over the faster 35mm. The DA 35mm is an excellent lens for a great price. Sigma has a 28mm 1.8, again a larger lens.

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Dan