The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 16-35mm F2.8L III and the Sigma 10-20mm F3.5 EX DC HSM 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. Canon 16-35mm F2.8L III is the longer of the two lenses at 128mm. The Sigma 10-20mm F3.5 EX DC HSM with a length of 88mm, is 40mm shorter. Besides being longer, the Canon 16-35mm F2.8L III also has a larger diameter of 89mm compared to the Sigma 10-20mm F3.5 EX DC HSM's 87mm 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. Sigma 10-20mm F3.5 EX DC HSM weighs 520g, 34% (270g) lighter than the Canon 16-35mm F2.8L III's weight of 790g.
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
Both the Canon 16-35mm F2.8L III and the Sigma 10-20mm F3.5 EX DC HSM 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 10-20mm F3.5 EX DC HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Canon 16-35mm F2.8L III has a focal range of 16-35mm and 2.2X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 25.6 - 56mm.
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.