It’s really hard to come up with any kind of a solid digital-resolution-relatable number for any given film stock, if only because multiple layers of silver hal

It’s really hard to come up with any kind of a solid digital-resolution-relatable number for any given film stock, if only because multiple layers of silver halide grains randomly distributed in an emulsion across three dimensions has no direct relationship to a two dimensional matrix of regularly distributed pixel elements, but the MTF curve of the stock describes its theoretical limit of resolution in terms of line pairs per mm. There’s published MTF curves for every stock, but the limiting factor is almost always the optical system, not the stock. An 8x10” negative shot with a very slow, black and white stock (say PanF for telescopic astrophotography) would exceed the practical DPI capacity of any extant commercial drum scanner… at a somewhat informed guess FP4 would probably top out somewhere north of 6400 DPI, as I’ve seen those scans not pick up details visible through a really good high power loupe.