I recently used Microsoft Image Composite Editor to stitch this panorama together from scanned negatives. The film I used was Ilford Delta 100, and the camera is a Nikon FM with a 50mm lens. Each of the five frames were shot with the camera rotated 90 degrees (roll) on its ball mount (i.e. "Portrait style").
As you can see, the borders between the individual frames of the panorama are clearly distinguishable due to what appears to be tonal artifacts that present in the same part of the frame on each shot.
My question is this: What could be causing this tonal variation across the frame?
Should I be concerned about light leaking?
*Edit: I do not know how these were scanned, though that could be a likely culprit. I had them developed + scanned commercially.
IIRC I shot these at f/16, 1/160s.