The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Nikon 20mm f1.8G ED and the Rokinon 24mm f1.4 for their suitability to various photography scenarios:
Size and Weight Comparison
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Nikon 20mm f1.8G ED weighs 355g, which means it is 225g (38%) lighter than the Rokinon 24mm f1.4 which has a weight of 580g.
Both Nikon 20mm f1.8G ED has the Nikon F (DX) lens mount whereas the Rokinon 24mm f1.4 has the Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (DX) Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Rokinon 24mm f1.4 is also available in Canon EF , Four Thirds, Pentax KAF, Sony Alpha and Samsung NX mounts.
Nikon 20mm f1.8G ED is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 30mm.
Rokinon 24mm f1.4 is a prime lens with fixed focal lenght of 24mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 36mm.