The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.8 EX DG RF and the Canon 16-35mm F2.8L III for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Canon 16-35mm F2.8L III is the longer of the two lenses at 128mm. The Sigma 20mm F1.8 EX DG RF with a length of 90mm, is 38mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 89mm.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Sigma 20mm F1.8 EX DG RF weighs 520g, which means it is 270g (34%) lighter than the Canon 16-35mm F2.8L III which has a weight of 790g.
Filter Threads
Both the Sigma 20mm F1.8 EX DG RF and the Canon 16-35mm F2.8L III have the same Filter thread size of 82mm.
Below are links to the 82mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Sigma 20mm F1.8 EX DG RF and the Canon 16-35mm F2.8L III 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 F1.8 EX DG RF is also available in Nikon F (DX) , Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 20mm F1.8 EX DG RF 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.
On the other hand, the 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.