The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.8 EX DG RF and the Rokinon 14mm f2.8 for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Rokinon 14mm f2.8 is the longer of the two lenses at 96mm. The Sigma 20mm F1.8 EX DG RF with a length of 90mm, is 6mm shorter. On the other hand, the Sigma 20mm F1.8 EX DG RF has a larger diameter of 89mm compared to the Rokinon 14mm f2.8's 87mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Sigma 20mm F1.8 EX DG RF weighs 520g, which means it is 32g (5%) 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.
Ultra-Wideangle Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both the Sigma 20mm F1.8 EX DG RF and the 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.
Sigma 20mm F1.8 EX DG RF is also available in Canon EF , Nikon F (DX), Pentax KAF and Sigma SA mounts.
Rokinon 14mm f2.8 is also available in Canon EF , Nikon F (FX), Four Thirds, Pentax KAF and Samsung NX mounts.
Focal Range
Sigma 20mm F1.8 EX DG RF 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.
On the other hand, the 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 a 35mm (FF) equivalent of 21mm.