Actually the top left corner is the blue sky as
it appears when shot on Kodak Tech Pan film.
Tech pan is red sensitive and is great for dynamic
clouds, similar to using a red filter, or the red
channel in Photoshop. Not a flaw, but a feature
and that I utilize. It's hard to discuss tonality and
and D Max when looking at a digital image on a
computer screen. The truth comes out in the
final print.
Thanks for your explanation. Maybe you should take a photo of the final print, or a screen shot of the final image prepared for printing. I can only comment on what I see.
Vignetting, when it occurs, is not always consistent in all four corners. There appears to be no vignetting in the top right corner of your image, but there does appear to be vignetting in the extreme parts of the lower corners.
However, the fact that this is a shot from Kodak film explains the oddities. I apologize for missing your comment that the shot was from the 1980's. I'm so used to using digital cameras where any vignetting is automatically removed in Adobe Bridge.
By the way, are you still shooting in film? Do you see some advantage?