[BigMackCam]

The only way I've seen to get all of it accurate for a wide angle view is like BigMack suggested- use a "normal" perspective lens, the 43mm Limited on FF or a 28mm lens on APS-C, on a tripod, carefully pan 2 or more shots, and stitch them into a pano.

Agreed. For panoramic stitching (and I don't have a huge amount of experience with this, in fairness), I tend to work easily and get good results with the DA35 f/2.4 or f/2.8 Limited Macro, and the DA40 Limited (on my APS-C cameras)

[Madaboutpix]

Considering adding a wide angle prime. 1. Never purchasing a prime wide angle before, should I expect some image distortion with the 15mm? 2. Also, any general opinion on the above 15mm vs 21mm?

Back in 2013, when I was looking into which Pentax wideangle prime to get, I had the DA21 on my personal shortlist, too. But then, from as far back as the film days, I had been drawn to that 24mm-ish-FF-equivalency FOV. 28mm on film had always appeared to me as okay, but not really wide enough, yet I didn't want to go completely overboard with perspective distortion and volume deformation, which is why I picked up a Sigma Super-Wide II 24mm F2.8 for my Minolta X-700 and fell in love with it. Later, on my Sigma SA-9, I shot a 24-70mm zoom, which offered the same FOV at the wide end.

In Pentaxland, the closest to what the Sigma Super-Wide had given me was the DA15, except that it did the job even better. Perhaps more field curvature, but definitely better microcontrast, those beautiful Pentax colours, remarkable flare resistance (where the Sigma, well, kinda sucked), Limited build quality, almost negligible barrel distortion (where the Sigma exhibited the somewhat ugly mustachio type), and those beautiful starbursts (smc-DA version).

Ultimately, only you can decide if you're gravitating more towards a pronounced or a moderate wideangle, which the DA21 would give you. If you got the DA15 first, you would leave the door open to get something like the DA21 later, unless you opt for the arguably even more attractive HD DA20-40.

Despite its fairly slow widest aperture of F4, at least in my photography, the DA15 has proven a wonderfully versatile performer, regardless of whether I threw architecture, interiors, landscapes, or even family-journalism subjects at it. It's one of those lenses that can pull you into the Pentax APS-C system. The attached images should give you some idea of what this lens can do:

[bassek]

I have the DA14 and the HD DA21. The DA14 excels indoors, however it suffers in bright daylight. The DA21 is yet to be tested in bright light.
I suppose a surf&snow setting would help, what settings for these wide lenses have you preferred?

Seb

[rptdc]

I just thought of another decision factor specifically for me as comparison from my last camera.

My Lumix LX100 had a zoom range of 10.9 - 34 at 4:3 crop, which I think would be a 22 - 68 mm full frame range? If this is accurate, I very frequently used the wide end of this range, 22mm. So if I went by my previous habits, the Pentax 15 mm (apc crop factor of about 22mm for comparison?) would be the best choice for a FOV that I frequently use.

Are my calculations close?

[RGlasel]

Are my calculations close?

Very close, on Panasonic's website, the 35mm equivalent focal length range is 24mm - 75mm. I checked with a DOF calculator, wide open with the Lumix at 11mm and a subject distance of 4 meters (13 feet), everything from 2.16 meters to 23.78 meters (basically 7 feet to 100 feet away) should be in focus, with the DA 15 wide open, you will have everything from 1.66 meters to infinity in focus. But at that wide of a field of view, you probably don't care if the Lumix produces a slightly shallower depth of field and the K-70's sensor is a big upgrade. Personally, I think the DA 15 Limited is a great lens for squeezing more of a scene into the frame and as I mentioned before its flare resistance is phenomenal. But you have to accept lots of field curvature and the inevitable distortion of squeezing double the field of view of a "normal" lens into the same frame. Any photograph distorts what our eyes see, but I really like the distorted photographs I take with the DA 15.