If there’s one aperture that I use more than the rest on my Fujifilm X100F, it’s f/4. It seems to be the sweet spot, with corner-to-corner sharpness and maximum sharpness in the center. Bokeh is quite nice, although not heavily pronounced. It has enough depth-of-field to be useful in almost any situation. It seems like the best all-around aperture on this camera.
Some of my favorite images were captured with the aperture set at f/4. I use it for street photography, still-life, family snapshots, landscapes–anything really. It’s large enough for use in low-light situations and small enough for bright-light scenes. It’s a good set-it-and-forget-it option. If I could use only one aperture on this lens, f/4 would be my choice.