You can now preorder the recently announced NiSi RF 15mm f/4 Sunstar. A compact and unique offering for Canon's RF mount.
Unique Aperture Design.
The NiSi 15mm f/4 Sunstar Super Wide Angle Full Frame ASPH Lens features a unique aperture design that contains 10 straight blades allowing for Sunstars from f/4 to f/22 and optimal image quality throughout. This breaks the paradigm of requiring a small aperture to create a Sunstar.