Portrait Lens Options: Fuji 90mm F2 vs Sigma 50-100 F1.8 w/Fringer

I wonder about this too. I've been interested in the Sigma 50-100 for a while now, and I used to have the 90 f/2 as well as the Sigma EF 18-35 with the Fringer, both used with my X-H1.

First, about the 18-35. Long story short, I ended up selling it and getting the 16-55 2.8. Sigma was sharp (faultless to my eye, really) but I didn't love it. I wouldn't swear on it, but to my eye, it produced "flat," two-dimensional images. This could be due to the complex optical construction, or perhaps it was just in my head, but I couldn't get past it. The AF worked as well with the Fringer as it does on Canon cameras--quick and accurate, but I did not use AF-C much so I can't comment on that. Still, that experience made me hesitate about going for the 50-100, and I would really have to try it out before committing to it.

The 90 f/2 was flawless. It is sharp wide open and makes really nice bokeh. I also have the 56 f/1.2 APO, and I would consider them comparable in this respect, but I don't spend time pixel-peeping the blurry parts. Most importantly, the 90 had that 3-D magic, if you believe in that sort of thing. The clanky AF was weird at first, but once the camera is switched on, it is simply amazing. I ended up letting go of it because I just did not use that FL enough, but I do regret it now and then when I look at those images. I will say this: despite its stellar reputation, this lens does not get much love on the used market (maybe because of the limited usefulness of that FL), so it pays to get a nice, used copy if you end up going that route.