The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 20mm F1.8 and the Rokinon 35mm f1.4 for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Rokinon 35mm f1.4 is the longer of the two lenses at 112mm. The Samyang 20mm F1.8 with a length of 88mm, is 24mm shorter. On the other hand, the Samyang 20mm F1.8 has a larger diameter of 83mm compared to the Rokinon 35mm f1.4's 63mm diameter.
The 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. Samyang 20mm F1.8 weighs 497g, which means it is 163g (24%) lighter than the Rokinon 35mm f1.4 which has a weight of 660g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Nikon F (FX) Mount for size comparison purposes.
Wideangle Prime Lenses in Nikon F (FX) Mount for Size Comparison
Both the Samyang 20mm F1.8 and the Rokinon 35mm f1.4 has the same Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (FX) lenses are Nikon D6, Nikon D780 and Nikon D3500.
Samyang 20mm F1.8 is also available in Canon EF , Canon EF-M, Fujifilm X, Micro Four Thirds, Pentax KAF, Samsung NX, Sony Alpha and Sony E mounts.
Rokinon 35mm f1.4 is also available in Canon EF , Four Thirds, Pentax KAF, Sony Alpha and Samsung NX mounts.
Samyang 20mm F1.8 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 a 35mm (FF) equivalent of 30mm.
Rokinon 35mm f1.4 is a prime lens with fixed focal lenght of 35mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 52.5mm.