The Samyang 24mm T/1.5 (f/1.4) offers a full-frame wide angle view for the Sony A7/A7R (the Sony Zeiss 24mm f/1.8 Sonnar covers only the APS-C frame for NEX cameras, not full frame). As a DSLR lens with a telecentric design, it does not have any ray angle issues.
It is a manual focus lens with fully manual aperture control—perfect for some types of shooting, inconvenient for others. It is not “chipped”—the camera does not know which lens, which aperture, etc; no EXIF data is communicated. Which is the same as mounting any lens via lens adapter.
Readers know that I prefer my Zeiss lenses for just about all of my shooting.
But the Samyang 24mm T/1.5 Cine lens has impressed me as offering very good image quality on the Sony A7 at a very affordable price—it’s a true value. The Nikon 24mm f/1.4G might not be any better ( I have not shot the Nikon 24/1.4G on the Sony A7 and the 24/1.4G would require the hassle of an electronic adapter). Moreover, the Nikon 24/1.4G costs considerably more, has an inferior focus ring, no manual aperture control and requires a lens adapter.
One might ask how it compares to the Sony Zeiss FE 24-70mm f/4 OSS Vario-Tessar, and I might “get there”, but f/1.4 is hardly f/4, being three stops slower and thus inapplicable for many types of shooting, such as indoors (image stabilization is not a substitute for shutter speed when the subject is moving!).