I’ve used about a dozen of my Canon lenses on the GFX50R with the TechArt adapter, including the TS 45. Although I haven’t done exhaustive testing, the initial results have been excellent with most of the L glass if you don’t mind the autofocus speed. My best results have been with the 85/1.2, 50/1.2, and the 70-200/2.8. Almost all have some vignetting of course but for most I can correct it in PS.