I had some difficulty determining the entrance pupil of the Sigma DP2 Merrill due to its awful low-res rear LCD; close but not perfect, and that’s a parallax headache at close range [doing it precisely requires iterative tests to verify the best possible position down to 0.5mm or better).
Fortunately, Photoshop did a fine job of merging the frames into this 56 megapixel stitched image, created from six vertical images. It could print very large, even the JPEG-derived version used here (I’d use the raw images normally, but in the car with a laptop...).
More difficult is anticipating the ending composition that results after merging the images made with rotational stitching; the image feels unbalanced. I also had very little working room, so it wasn’t possible to frame much differently that done here.
Stitching 3 frames made with a shift lens is much more straightforward, but to this day there is no shift lens on the market that delivers more than “good enough but uninspired” performance. Moreover, a shift lens generally yields a 2X gain in pixels with much reduced quality at the periphery, but this 6-frame composite is about 3.5X more pixels than a single frame. Had I the working room, I could have moved back and shot with the DP3 Merrill as a dual-row, yielding ~110 megapixels or so (Really Right Stuff sells a special stitching setup for such things, which I used here; it allows using any camera angle while rotating on-level).