The AF-S 28-70 indeed has its own aperture ring on the lens, and that will be how you want to set the working aperture.
This means that you do not necessarily NEED an adapter for G-type lenses (that comes with a rough control ring on the adapter), but there is no obvious reason why your lens would not work with a G-type adapter (which normally works with both F and G type lenses).
Just set the ring on the adapter to allow for the largest aperture opening (check this visually with the unmounted lens set to f/2.8) and leave it there...
Or, alternatively, use the ring on the adapter to easily switch between fully open aperture (for precise manual focusing) and the shooting aperture set on the lens.
There's two reasons why you won't find a tit, shift or tilt&shift adapter to use Fuji XF/XC lenses on Fuji X cameras:
the imaging circle of the lens MUST be a lot larger than the (APS-C) sensor size, to make extra space available for the sift and tilt movements (T/S adapters vor Nikon, Canon etc. lenses only work with full-frame lenses);
as stated above: as XF/XC lenses are designed for the 'right'flange focal distance for X cameras, there is no room left to physically accommodate for the tilt and/or shift mechanism.
It is (at least theoretically) possible to devise an adapter with additional optics to handle the trick. Such an adapter should enlarge the imaging circle (more like a teleconverter, and the opposite of what a Speed Booster does), as well as compensate for the extra physical length of the device. A good example is Hasselblad's HTS 1.5 adapter (for using Hasselblad lenses on Hasselblad bodies), that introduces a 1.5x 'crop factor' and a 1.3 stop aperture reduction.
I can confirm that using a DSLR full-frame lens with e.g. the Kipon T&S adapter is a good tool for occasional use. If your requirements are higher, get a Canon, Nikon or Samyang full-frame 'real' tilt&shift lens. Using one of these with a Speed Booster even maintains the wide angle of view, when that is important (architecture, interiors, landscape).
You don't need a G-type adapter if you are only using lenses that have their own adapter ring. But one with such a (simple) ring can be very helpful for the approach veejaycee suggests: set your working aperture on the lens, and use the control ring on the adapter to switch between fully open (compose and focus) and closed to working aperture (shoot).
I am very pleased with my simple Kipon adapters. The Novoflex one is more expensive, but better finished and has an optional tripod collar mount. The F-version of the Metabones is also mechanically excellent and has an Arca-compatible tripod socket.
And there's the Speed Booster for F and G lenses, of course.
That would surprise me... Have you tried to rotate the lens mount? It should cover a full 360 degrees, with 30 degree click stops.
The tilt and shift directions however remain at a fixed 90 degrees with respect to each other (like Nikon PC-E lenses and older Canon TS-E models). Newer Canon TS-E models and the Samyang 24mm T/S allow for independent setting of these directions.
If you have G-type Nikon lenses that don't come with an aperture ring (including DX lenses) you will need an adapter with its own control ring. Aperture setting will be very crude. Something like the Kipon NIK G - FX will do. The Novoflex FUX/NIK has a better finish and a smoother control ring. It also can be combined with an optional tripod collar (ASTAT-MFT) which comes handy for heavier and longer (tele, macro, zoom) lenses. But there's an extra bill to cover...
If all your Nikon lenses have their own aperture ring, then a cheaper Kipon NIK F - FX will do, or the Metabones N/F-X which has a (smaller) tripod mount.
Metabones' Speed Booster for Nikon G comes with a much more usable aperture control system. I would not be surprised at all if a new 'glass-less' Nikon G adapter would appear soon with the same type of ring.
I do indeed own all five current models of the Kipon Nikon to Fuji X adapters, as well as a few from Novoflex and Metabones (the last one came in days ago and is not yet in the above picture).
If you intend to (also) use Nikon G-type lenses (without their own aperture ring) then you must use an adapter with an extra control ring: that will let you "control" the aperture in a crude and not so precise way. The Kipon G adapter (€68) works fine. The much more expensive Novoflex FUX/NIK one (€169) has a better finish, a smoother aperture control ring and an optional tripod mount collar (€89 extra).
If you only plan to use F lenses (non-AI, AI, AI-s, AF, AF-D) having an aperture ring, then a simple "straight" adapter like the Kipon F (€57) is all you need. Of course a G-type adapter will work as well, with the added option to use the extra control ring to quickly move from wide open (for focusing) to the working aperture set on the lens (for shooting). If you own a few longer/heavier lenses (such as tele or macro ones) you might prefer an adapter that comes with a tripod attachment, such as the Metabones one (€128) or the above-mentioned Novoflex combo.
The Kipon shift-only (€80) or tilt&shift (€284) adapters support F-type lenses only. You could use them as "regular" adapters; with the tilt&shift adapter however, the bulk and the risk of inadvertently adding a tilt and/or shift may make this more of a theoretical than a practical case.
I found the Kipon tilt-only adapter (€104) only useful for creative focus applications (lensbaby style) with F-type lenses.
All prices indicated are what the adapters ended up costing me when ordering online (Kipons through ebay, Novoflex/Metabones directly from the suppliers) including shipping (to belgium), taxes and other charges.
@jac: I used LR4.4 for post-processing, and the amounts of vertical correction applies were +1, -3, +17 and (obviously) 0 respectively.
I try to avoid big corrections by thinking carefully while shooting how to hold the camera (even when I shoot without tripod, as was the case on this trip).
When the situation forces me to tilt the camera, I will frame with extra room to compensate for the crop after correction (e.g. with the third stairway picture), or try to use the convergence creatively (as with the last shot).
Just a little on the first one above, to compensate for vertical perspective distortion, virtually nothing on the others.
The most important thing however: there's so little barrel distortion that you can as good as forget about it. The images shown here all start from RAF file, so uncorrected by the camera or Lightroom, and I have never been tempted to try more than a +1 distortion correction value.
Shooting handheld (no tripod, no bubble level) with a 21mm equivalent wide angle of course forces you to think constantly about camera position and orientation, as perspective distortion lies just around the corner...
I have a few other shots (perhaps for a future post) where due to the cramped space I had no choice but to point my camera upwards. Lightroom's perspective control tools work excellent to fix those cases. The 14mm has a wide enough filed of view to plan from the start for the unavoidable frame cropping that comes with software correction, and its sharpness and microcontrast are high enough to avoid any visible problems in the final image.