Here is the Canon Cinema EOS C500 Mark II


EF 800L
May 29, 2019
You have the internal ND filters. Maybe they aren't small enough to fit with RF mount?
That is almost certainly the case. There isn't much room between the back of the lens and the sensor with R (probably almost none with some lenses). Also, this is a cinema camera and most users are going to be looking at parfocal lenses, so not much real interest in R glass. Lastly, the ultra fast wide angle advantage of the R mount does not relate to a significant percentage of cinema work. In any case, running the rapids is more likely to be shot with a disposable body than a $16k studio camera.