A very common use case for tilt is pan focus, or "getting everything in focus". There are other reasons for using tilt that are not about pan focus. For example, you might want to use background or foreground blur as a compositional device, but you want to control where the plane of focus is in the image to control what parts are blurred.
In this post, I show a few examples to illustrate what I mean.
In this first image, I wanted the plane of focus to run along the lip of the waterfall so that the edge and face of the waterfall and that little plant at bottom-left would all be acceptably sharp. A bit of swing (sideways tilt) let me do that. If I'd shot it straight on (no tilt), neither the plane of focus nor the background blur would have been what I wanted.
Mamiya G 150mm f/4.5 L on my MAB Camera with GFX 50R. I didn't record the aperture, but it was probably f/8
In this second example, I wanted an angled viewpoint on this rock (so not straight down from above). I also wanted the blue rock to be in focus, and the red rock underneath to be softer. A bit of tilt let me place the plane of focus parallel to the blue rock's surface, blurring out the underlying red rock. The wedge of acceptable sharpness wasn't thick enough to get the visible side of the blue rock, but I'm still happy because it got the face and a bit of the top edge. With this perspective, focus stacking simply would not have worked. Had I been shooting straight down, focus stacking would have worked well.
Schneider-Kreuznach APO Componon HM 90mm f/4.5 with MAB Camera and GFX 50R, probably f/11
The scene in this third image is a similar situation as the above image, in that I wanted the plane of focus to run over the top of the stones so that the water, the leaves, the stones and the pine needles were all in focus and sharp. Locating the plane of focus across the top level of the scene would leave the lower left section out of focus, which I liked. I didn't quite get the leaves at upper-left in the wedge of acceptable sharpness, but they are at a slightly lower level than the two yellow leaves, and in the shade, so I'm happy enough.
Schneider-Kreuznach APO Componon HM 90mm f/4.5 at f/11 with MAB Camera and GFX 50R
For me, this is a big part of what tilt is all about. In each of these images, I wanted the plane of focus in a specific location as part of the design of the image.
When I can't have this kind of control, I can't make the picture the way I want to make it. I find that very limiting. There's a reason I only have one native lens for GFX, and almost never use it. It doesn't let me do what I want.
