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 Canon 28mm 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. Sigma 20mm F1.4 DG HSM A is the longer of the two lenses at 130mm. The Canon 28mm f2.8 with a length of 43mm, is 87mm shorter. Besides being longer, the Sigma 20mm F1.4 DG HSM A also has a larger diameter of 91mm compared to the Canon 28mm f2.8's 67mm 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. Canon 28mm f2.8 weighs 185g, 80% (765g) 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 Canon EF Mount for size comparison purposes.
Wideangle Prime Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Sigma 20mm F1.4 DG HSM A and the Canon 28mm 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.
Sigma 20mm F1.4 DG HSM A is also available in Nikon F (FX) , Sigma SA and Leica L 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 1.6x crop, it provides a 35mm (FF) equivalent of 32mm.
Canon 28mm f2.8 is a prime lens with fixed focal lenght of 28mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 44.8mm.