Nice shot and everything other than the lower corners is 100%. So the 60mm lens was used throughout the roll with a filter but the vignetting only occurred on the last two images? I was going to suggest that as 60mm is wide angle then that may be the reason but given that 60mm is only slightly wide I'd have thought that one filter on a 60mm is OK and anyway if the answer to my first question is Yes then that rules out the filter
Was the filter used on the 60mm in the past with no issues?
@pentaxuser Yes! It is my favorite lens, been using it for 2+ years. If it were the typical vignetting issue I would expect to see it in the top corners also . . . ???
Wondering if it a film or processing issue, it is my first roll of a newly introduced film that is marketed as similar to the old Kodak Panatomic X . . . there is a thread about it in the Industry News sub forum . . .
ETA: The lens needs a CLA, the focusing ring is stiff but the f stops work very smoothly. This lens was made in the 1950s so it is at least 70 yrs old. Pretty sure it is NOT the lens because this is the first time I have seen this issue.
I had the same problem with my 50mm Hassleblad lens using a screw in filter and the 50mm screw in sun shade. The filter moved the sun shade forward just enough to start vignetting the corners, the sun shade is round, use serious 7 filters with the shade now.