As a longtime/dedicated Pentax user, I'm a little ashamed to admit that I'm just now finding out about this release - somehow this flew under my radar.
I literally have one of almost every Pentax screwmount camera made (including Pentax S), have most every lens up until the FA plastics... and currently am shooting with K1/K3/K5 iis. I mention this back story because I spent the weekend shopping for Sony a7R iv / a7R iii cameras and lenses- precisely because I don't feel that the available Pentax UWA (specifically 20mm) FF lenses really support the K1 36Mp focal plane. Before shopping for Sony over the weekend, I retested my Pentax 20mm lenses and confirmed that they're very sharp in the center, but very soft in the corners on FF (at f/8 'sweet spot'). I shoot a lot of UWA images, interiors, architecture, and while hiking. Many\most successful UWA shots utilize foreground objects to create interest, sense of scale, etc, so soft corners will ruin a large percentage of otherwise well-composed images. Maybe I have unique needs, but for me, this lens is literally the difference between abandoning Pentax and staying the course (that I've been on for 40 years).
For interiors, I already have an excellent Venus\Laowa 12mm f/2.8, so I would use this 21mm primarily for hiking (where 12-14mm is just too wide). Since I'd be carrying this on my back for many miles, I'd not only welcome, but will be elated, if it is f/4 versus 2.8! The world really doesn't need any more big, heavy UWA f/1.8 primes.
Now, if the Sony 61Mp sensor makes it into the next Pentax FF, I'll be set for the next decade or so!
Last edited by Starpacer; 02-15-2021 at 02:18 PM.