What has this to do with anything
Links to a Zucchero track

I'm giving this one a miss..... I'll wait until they bring out
a 35mm f/6.3 with just 2 elements

What everyone seems to be missing about this lens is that 35mm is the STANDARD LENS for Pentax digital just as 50/55mm was the standard for 35mm cameras.

You have to go back to 1957 for the last time that Pentax sold a standard lens that had a poor f/2.4 as it's widest aperture. It was the first 58mm lens for the newly designed Asahiflex link It was replaced 3 years later with an f/2.2 design. Other manufacturers rarely produced anything smaller than f/2.2 as their standard lens. So why they have produced this is baffling?

Hopefully it will perform better than what the f/2.4 part of the design brief seems to indicate.

Gorgeous shot.... looks so peaceful.
Welcome to the forum.

Whilst quite technical this site has some useful information on it about FF v crop sensors link

There is a site that's been posted on here that shows the relative sizes of each sensor.

What the video doesn't show is that his head would be the same size on both sensors, there would be more of the space surrounding him on full frame.

PM sent re: Pentax DA* 300/4

We've always known that on Pentax the difference is 50% Not a very good demo because he's made the frame sizes the same.

It would cause problems with say 400mm lenses you would need to buy a 600mm lens to get the same frame on FF as APS-C. Then if you used the 600mm lens on APS-C you fill the frame better with say birds.

Should be. The moon would probably be better

There is a method where another camera with a lens known to focus on infinity accurately can be used as a collimator to set up a 2nd camera and lens to infinity. See here

People managed OK with the ME-F focussing by just the green light and beep.