The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony 20mm F2.8 and the Rokinon 14mm f2.8 for their suitability to various photography scenarios:
Size and Weight Comparison
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 Sony 20mm F2.8 with a length of 54mm is 42mm shorter. Besides being longer, the Rokinon 14mm f2.8 also has a larger diameter of 87mm compared to Sony 20mm F2.8's 78mm diameter.
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. Sony 20mm F2.8 weighs 285g, which means it is 267g (48%) 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 Sony Alpha Mount for size comparison purposes.
Wideangle Prime Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both Sony 20mm F2.8 and Rokinon 14mm f2.8 has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A99 II, Sony A68 and Sony A77 II.
Rokinon 14mm f2.8 is also available in Canon EF , Nikon F (FX), Four Thirds, Pentax KAF and Samsung NX mounts.
Focal Range
Sony 20mm F2.8 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 an 35mm (FF) equivalent of 30mm.
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 1.5x crop, it provides an 35mm (FF) equivalent of 21mm.