Thank you for your detailed answer, Chris! Of course, I've already read many posts here in the forum regarding WA. Unfortunately, it seems no one(!) uses the WACP-C with the 24-50 or the 15-30 STM, or at least I can't find any reviews of it. I've also read DreiFish's excellent posts, but as you mentioned yourself, he only evaluates the 24-50 with the WWL-C. A friend uses the WACP-C on a 5D4 and an old 28-70 (if I remember correctly) and is very impressed compared to the 8-15/4. Perhaps his statement made me too optimistic that I would have significant optical advantages with the WACP-C compared to my 8-15/4 setup. Does anyone here in the forum use the 28-70 (28-80) with a WACP-C? I haven't found any comments on that, at least. Unfortunately, I don't understand this statement - could you explain it again in other words? In my opinion, my only option with the R5 is to use the RF/EF adapter, the Kenko TC and then the 8-15/4 lens. Or do you mean I should replace the Kenko with a Canon RF 1.4x teleconverter (that I already own), then an extension tube and then mount the 8-15/4? Wouldn't I lose focus at infinite distance? Or would that be irrelevant because of the projection in the dome port? But maybe I misunderstood you completely... Thanks for that comment – I hadn't read any reviews yet and, based on Nauticam's recommendation of this lens for WACP-C, I assumed the optical performance was at least acceptable. By the way, I immediately cancelled my order for the 24-50 with my dealer this morning. 😉 Okay, I'll take note of that. 😁 I already read that the 140mm FE dome would be a very good choice for the 8-15/4, but I find it astonishing that it actually performs better than a superdome. I still have no choice using a superdome when it comes to split shots... To be on the save side: is it this one? Nauticam | 140mm fisheye port with removable shade (N120) | PanOceanPNauticam | 140mm fisheye port with removable shade (N120)...House of Underwater Photography | Nauticam | 140mm fisheye port with removable shade (N120 | authorized Nauticam Dealer in Germany | FREE SHIPPING within th I've already sold it. 🙄 I'm too much of a pixel peeper to be satisfied with the 14-35/4 lens and the 8.5" acrylic dome port combination. Even back then, with my 5D4, the EF 16-35/4 and a 230mm superdome, the corners didn't look that great, and behind the acrylic dome port it'l be even worse. Finally I think I'm now somewhat disillusioned about finding a (reasonably handy and affordable) system that will offer me significantly better corner performance. WACP-2 or FCP are out of reach, financially and in terms of weight.