Sigma 50-100mm f/1.8 + Fringer: How good is the AF?

While it's not quite the optical wonder that its little cousin, the 18-35, is it's also pretty darn close. Compared to the 50-140 which I'd consider one of Fuji's best zooms, the 50-100 cleans it's clock. There's also no free lunch. The 50-140 is a very lightweight lens especially when compared to most other 70-200 equivalents. It is as good as other manufacturers 70-200 f4 lenses but I don't think it's much to compare to any modern 70-200 f2.8 example despite but the price point might make you believe. Just like the 16-55 it's Fuji tax in all its glory. As compared, the Sigma is an absolute tank in both weight and girth. As opposed to the plastic fuji the Sigma is not only built like a German tank with a metal shell, it is also pushing a lot more glass at over a step faster. The other negative is that Fringer is unable to communicate focus speed and sensitivity settings from a Fuji body to the lens so the settings do nothing. Good news is that it's very snappy for most things. Bad news is that I won't pretend to say it is as fast or adjustable as the fuji 50-140. At the end of the day you are getting state of five years ago AF tech with Fuji bodies so giving up a little can pinch a little harder with an adapted lens but if your demands were lightening fast AF you'd be somewhere else anyway. So for the end result of what the sigma delivers optically and the price I'd say it's a no brainer, especially if you are much more into photo than video. Plus it's going to cost you quite a bit less.