Observation: The 15mm Panny in a vertical position has a horizontal field of view not so unlike the 75mm on the Pentax, horizontally. Then, to imitate the comp while the film awaits processing, all I need to do is crop a 5×4 out of the vertical frame.
Why? Well, and this is a bad answer, the film hasn’t been processed.
As for metering light like this, it remains to be seen how the expired–for–more–than–a–decade–ago Astia takes it.
Stay tuned! (Actually, don’t)