One degree of tilt...
Here is an exemplar image showing what tilt can do. First off, the light was changing fast and so I had to move very quickly to get this before the rainbow disappeared -- so it is not framed ideally, and in fact this a crop from the full IQ180 frame to get the old ruin and the bow out of the dead center. Anyway, the crops are still full size and work for the purposes of this example.
First, the cropped full frame image -- about 20MP taken off the top and LH edge of frame:
Specs for the shot were early AM light and rain, 40HR-W at f8, 1/30th at ISO 35, 10mm RISE and 1 degree forward tilt to hold foreground through infinity sharpness at f8. LCC was taken and image was processed in C1, then adjusted slightly for contrast in PS before creating the web crops and jpeg.
Here is the crop from about two feet in front of my right tripod leg:
Here is a crop showing ground level at mid frame distance , as well as the structures there, as well as the far mountain in decent light (and no rain) at infinity:
Note: There is a slight "hot spot" mid frame near the base of the rainbow. At first I thought this was due to the rain right there -- and it could be -- but I also had similar spots on higher contrast images taken the day before and day after this one. So right now, I am puzzled. I originally tested the lens in high-contrast light and did not get any hot-spotting, but now I do. Just realized it was raining most of the time, so perhaps I got some moisture in the internal surfaces of the lens, need to check that out ASAP...