The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 10-20mm F3.5 EX DC HSM and the Canon 20-35mm f3.5-4.5 USM 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 10-20mm F3.5 EX DC HSM is the longer of the two lenses at 88mm. The Canon 20-35mm f3.5-4.5 USM with a length of 69mm, is 19mm shorter. Besides being longer, the Sigma 10-20mm F3.5 EX DC HSM also has a larger diameter of 87mm compared to the Canon 20-35mm f3.5-4.5 USM's 84mm 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 20-35mm f3.5-4.5 USM weighs 340g, 34% (180g) lighter than the Sigma 10-20mm F3.5 EX DC HSM's weight of 520g.
Below you can find the dimension and weight table of the Wideangle Zoom Lenses in Canon EF Mount for size comparison purposes.
Wideangle Zoom Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Sigma 10-20mm F3.5 EX DC HSM and the Canon 20-35mm f3.5-4.5 USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Sigma 10-20mm F3.5 EX DC HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 10-20mm F3.5 EX DC HSM has a focal range of 10-20mm and 2.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 16-32mm when used on a APS-C / DX format camera. Canon 20-35mm f3.5-4.5 USM has a focal range of 20-35mm and 1.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 32 - 56mm.