Optical limits has tested the RF 24-105/f4. In summary: It shows it strong Iq at f4/24mm. With moderate barrel distortion. And pretty good IQ up to 70mm pretty much equalling the Canon 24-70 f2.8 v2 from 24 to 70 at f4. It bests the sony FE 24-70. Significantly in the corners at 24mm. Its like a 24-70 with another 71-105mm available, minus the So if you don't mind the adapter and have (or plan to get) a longer lens anyways, I think the 24-70 f2.8 mkii would be a good choice. Tmjc's gear list: Canon EOS R8 Canon EF 100mm f/2.8 Macro USM Canon EF 24-105mm f/4L IS USM Canon 70-300 F4-5.6 IS II Tamron 17-35mm F2.8-4 +2 more. BrHqmBQ.