Yongnuo’s release of an 85mm f/1.8 RF-mount lens with autofocus is interesting because it competes directly with what is likely Canon’s weakest RF offering, it’s 85mm f/2 lens whose image quality is merely adequate.
It is also interesting because images of the mount show that it is using a non-standard RF mount ring configuration, with a cutout in one of the three flanges.
The YN 85mm f/1.8R DF DSM lens has two side controls, one offering manual focus, and the other allowing for a declicking the detents of the focus ring, eliminating hard stops. It also includes a USB port for firmware updating.
Yongnuo has traditionally used out-of-patent Canon designs to offer cheaper versions of older lenses to the large Canon market. In this particular case, the older f/1.8 lenses Canon sold in the EF days may actually prove to be of better image quality than the more current RF f/2 design.