The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.4 DG HSM A and the Samyang 24mm f1.4 for their suitability to various photography scenarios:
Size and Weight Comparison
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 24mm f1.4 weighs 580g, 38% (370g) lighter than the Sigma 20mm F1.4 DG HSM A's weight of 950g.
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
Lens Mounts
Both Sigma 20mm F1.4 DG HSM A and Samyang 24mm 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.
Sigma 20mm F1.4 DG HSM A is also available in Canon EF , Sigma SA and Leica L mounts.
Samyang 24mm f1.4 is also available in Canon EF , Four Thirds, Pentax KAF, Sony Alpha, Sony E and Samsung NX mounts.
Focal Range
Sigma 20mm F1.4 DG HSM A 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.
Samyang 24mm f1.4 is a prime lens with fixed focal lenght of 24mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 36mm.