The two last seasons of "Dynasty" and "The Reunion" certainly were. :-(
Nope, shot on Film and later
edited on Video. That's a HUGE difference, there can be a HD release any day, because film material does exist.
S8 and 9 of Dynasty do already
exist in HD for some years by the way, as the film material was rescanned in HD and already used for the R1 DVD Release. If those weren't shot on film, they would
never look as good as they do.
And i really can't imagine for Buffy Season 1 being shot on video. It's HIGHLY unlikely.
Like with Star Trek TNG, it was much cheaper to edit in the FX later on video. But they would have to rescan the whole thingy and recreate the FX (special effects) for a HD release.
That happened with Star Trek TNG and the X-Files already.
Look out for example for "filmed with
Panavison Camera and Lenses" or such in the end credits. Those are always hints for FILM cameras and they are mentioned in every episodes end-credits of BH 90210 and Melrose.
So... both definitly shot on film, no doubt about that.
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edit: Just found the confirmation for "Buffy" on the IMDB page in the technical specs section as well (as i mentioned before):
Negative Format 16 mm film (1997-1998)
35 mm film (1998-2003) - remaining seasons.
Printed Film Format: Video (=edited on Video).
https://www.imdb.com/title/tt0118276/technical?ref_=tt_dt_spec
So, Buffy was completly shot on film as well, just on smaller film (16mm) in it's first seasons

("Camera Panavision Panaflex Gold II, Panavision Primo Lenses
Panavision Panaflex Platinum, Panavision Primo Lenses")