Brightin Star 11mm F2.8 II Fisheye Lens 182° Full Frame Ultra Wide Angle Manual Focus

Diagonal field of view on a full frame camera is only ~167 deg, significantly smaller than the claimed 182 deg. Brightin Star have been queried about the discrepancy but no response received. Vignetting wide open is strong, there is also a colour cast in the corners. However, the sharpness is ok, stereographic projection is pleasing, build is solid, and the rings well damped. Clickless aperture is not my preference. The push-on lens cap is tight, for now, but would have preferred a positive clip on mechanism, not just fiction to hold it on as this can loosen over time. Overall, other lenses such as the 7Artisans 10mm/2.8 II provide a wider (and closer to spec), at least as sharp, and similarly solidly constructed alternative, though at a slightly higher price.