Since adopting Fuji's X-system as my go-to camera system for day to day and paid work, I have collected a large number of the XF lenses. On this system I tend to have a preference for shooting primes but do use the zooms where I need the reach or for travel.
I have to say that I have been incredibly impressed by the construction quality of the lenses, the handling and optical performance. They seem to have a biting sharpness over the frame at optimum apertures that was pretty hard to achieve with full frame DSLRs, even on some of the very best lenses. The primes especially, seem to have very pleasing rendering of out of focus elements and transition from sharpness to blur. Being old-school to some extent, I do love the aperture ring that can simply be turned when holding the camera in a shooting position. Also, one of the best things about the analogue style controls on the camera/lens system is that you can sanity check and see your settings before even switching the camera on.
In my opinion, one of the best ever lenses I used on my full frame Nikon cameras was the amazing ZF.2 Zeiss 135mm f2 APO Sonnar. It has stunning sharpness, colour, out of focus rendering and handling. I was therefore attracted to the Fuji equivalent, the 90mm f2, so I bought it back in 2015. It has what I would call the "maturing" Fujifilm build quality, with water resistance and more defined and firmer aperture ring than the earlier lenses. As with most Fujinon lenses, it feels lighter than you imagine it should, but has lovely build quality with considerable use of metals. It is big by the standards of this system but not huge.....like a somewhat longer 56mm, and somewhat narrower than I thought it would be. When the lens is detached or the camera is off, a lens group, which I assume is a focus group, slides about inside like a weight sliding up and down a tube. When the lens is live the electromagnets of the linear motors must hold it in place. It feels a bit weird at first but focus is fast and deadly accurate. Here is the 90mm alone and on the X-T1 for scale.
I took this lens with me to Cornwall in October when I went camping with my son. I hadn't taken many decent images of him recently and really wanted to try and get a few....they grow up so fast! I thought it would make a change from the 56mm to have some extra reach. This is a lens which you can use as a conventional portrait lens; you just need to be further back than with the 56mm, but where it is also superb is a bit further back still where you can shoot a whole body portrait at wide aperture. The sharpness in the focal plane and relatively rapid fall-off into blur makes for great images with interesting perspective.
Sharpness at all apertures is astonishingly good. I have no way of measuring it objectively but I can see from viewing images at 100% that it is the sharpest of the Fujinon lenses, and they are all very good to excellent. This really is a lens where you base your choice of aperture purely on the depth of field you want. You do not have to consider spherical aberrations, focus shift, weakness at widest aperture or any other image degrading issues. It is so sharp wide open that there really is no discernible difference in IQ when stopping down. Perhaps technically it maxes out at f2.8 but there really is no real world difference, even on the pixel-packed X-T2. It really is very similar to the Zeiss.
Here are a few from the recent trip, from top to bottom; f2.8, f2, f2.8, f2.
It also makes for a landscape lens when a bit more reach or compression is needed.
Probably the only negative thing I can say about this lens is that it seems a bit more prone to flare than other telephotos I have used, even with its big lens hood, but for me this isn't a major issue and it is fairly easy to avoid.
Here is an example with a straight out of camera jpg from a +EV exposure bracket that shows a green flare.
Some complain that it should have image stabilisation....I would rather take the lighter weight, smaller size and less complexity of a non IS lens in this class. I agree it is very useful on the likes of a 70-200 equivalent.
An obvious question would be how does it compare to the 50-140 f2.8 at 90mm. I haven't carried out side by side comparisons but I have that lens and it is definitely outstanding for a zoom. Aside from being a stop slower in aperture, the zoom doesn't have quite the IQ across the image field (still great though) and the bokeh is quite different most of the time. The zoom has a slightly busier, more swirly bokeh with tighter bokeh balls or bubbles, which is arguably not quite as pleasant as the smoother wide aperture rendering of the 90mm.
While it is not a macro lens, it performs very well at or near minimum focus distance and works well for flowers, destroying complex backgrounds.
Two to finish. First a portrait at f2. While this wouldn't be my normal choice for any street photography due to the way I like to shoot, it does make a compelling lens for isolating a subject or cropping into a busy scene.
Overall, an amazing lens. It may not be a focal length everyone can make use of, but if you can it surely must be be the current IQ champion among a range of outstanding lenses.