It may just be the best adapted FF lens on the Fuji GFX - The Tamron 45 f/1.8 SP.

Tamron's SP lenses are quite famous in the small but dynamic GFX adapting community. Known to punch way above their weight when it comes to sensor coverage these lenses are quite popular. Using the lens for well over a decade on three different systems (Canon EF, Panasonic LUMIX L, and GFX) I've had some mixed feelings about it. Loved it for FF, preferred the SIGMA 50 f1.4 for Mirrorless, and didn't always like the wide FOV on medium format. However, these issues are mostly subjective. An objective review of its capability reveals an "almost GF lens". Coverage is excellent, suffering only minor corner degradation and recoverable vignette at all aperture settings. A classic 35mm FOV combined with a wide f/1.8 aperture and nice rendering creates good subject separation and "3D pop". Mechanically coupled, long throw focus ring helps with precise manual focusing. AF is no slouch, and there is a nice bonus of extremely close focusing ability (for this lens class at least) HIghly recommended! 00:00 Tamron 45mm f/1.8 SP: Introduction 03:41 Coverage 04:58 An important lesson 06:20 Adapting FF lenses is a sensitive practice 07:44 Sample images 09:08 f/1.8 rendition 10:23 Fringing 11:25 Sharpness at f/4 12:15 Landscapes at f1.8 13:47 Action and motion 17:35 Distortion 19:21 Corner sharpness 21:04 Corner degradation in real life 22:59 Distortion 2.0 23:39 Slow shutter speed and IBIS 24:53 Details at f/2.2 25:26 Bokeh Quality 26:15 Direct sunlight 26:55 Frame-wide sharpness at slow aperture setting 28:01 Close focus (Macro-ish) 29:22 conclusion