Canon 300/F4 on GFX100 with Techart adapter, manual focus, 1/250, F8, iso250. No sharpening, exposure+1.5, shadow+100, contrast+30

A 20yr old full-frame lens shows slight vignetting in the corners, much reduced at F8. Cropping the top and bottom edges will leave a reasonable image (with sharpening and chromatic correction of the red fringing along the extreme edges, see bottom image).

Left edge of image, 300%, after DeNoiseAI