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 Sigma 35mm F1.4 DG HSM for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sigma 35mm F1.4 DG HSM is the longer of the two lenses at 94mm. The Sony 20mm F2.8 with a length of 54mm is 40mm shorter. On the other hand, the Sony 20mm F2.8 has a larger diameter of 78mm compared to Sigma 35mm F1.4 DG HSM's 77mm 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 380g (57%) lighter than the Sigma 35mm F1.4 DG HSM which has a weight of 665g.
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 Sigma 35mm F1.4 DG HSM 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 35mm F1.4 DG HSM is also available in Canon EF , Pentax KAF3, Sigma SA, Nikon F (FX) and Leica L 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.
Sigma 35mm F1.4 DG HSM 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 an 35mm (FF) equivalent of 52.5mm.