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 14mm f2.8 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 14mm f2.8 is the longer of the two lenses at 96mm. The Samyang 20mm F1.8 with a length of 88mm, is 8mm shorter. Besides being longer, the Rokinon 14mm f2.8 also has a larger diameter of 87mm compared to the Samyang 20mm F1.8's 83mm 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 55g (9%) lighter than the Rokinon 14mm f2.8 which has a weight of 552g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Canon EF Mount for size comparison purposes.
Wideangle Prime Lenses in Canon EF Mount for Size Comparison
Both the Samyang 20mm F1.8 and the Rokinon 14mm f2.8 has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Samyang 20mm F1.8 is also available in Canon EF-M , Fujifilm X, Micro Four Thirds, Nikon F (FX), Pentax KAF, Samsung NX, Sony Alpha and Sony E mounts.
Rokinon 14mm f2.8 is also available in Nikon F (FX) , 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 1.6x crop, it provides a 35mm (FF) equivalent of 32mm.
Rokinon 14mm f2.8 is a prime lens with fixed focal lenght of 14mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 22.4mm.