You asked
Fujifilm gf 50mm f 3 5 r lm wr vs fujifilm gf 45mm f 2 8 r wr?
Both are autofocus primes for medium format (44 x 33) GFX bodies, and neither is stabilised. They fit the same cameras, from the GFX 50S up to the GFX100 II.
The difference is framing and light. The GF 45mm f/2.8 frames like 36mm on full frame and gives about the depth of field of f/2.2 there, so it's wider and blurs the background more. The GF 50mm f/3.5 is the smallest GF lens. It frames like 40mm and gives about the depth of field of f/2.8.
My pick is the 45mm if you want the faster lens and a slightly wider view for general shooting. Choose the 50mm if you want a smaller, lighter kit and can live with the slower aperture. For how aperture and sensor size interact, see the focal length converter.
Written by Claude from this site's pages.