The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-35mm F1.8 DC HSM 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 18-35mm F1.8 DC HSM with a length of 121mm, is 7mm shorter. Besides being longer, the Canon 16-35mm F2.8L III also has a larger diameter of 89mm compared to the Sigma 18-35mm F1.8 DC HSM's 78mm diameter.
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Below you can find a scaled side-by-side image of Sigma 18-35mm F1.8 DC HSM and Canon 16-35mm F2.8L III to get a better idea of how their sizes compare in real life.
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. Canon 16-35mm F2.8L III weighs 790g, 2% (20g) lighter than the Sigma 18-35mm F1.8 DC HSM's weight of 810g.
Filter Threads
The Sigma 18-35mm F1.8 DC HSM has a filter size of 72mm whereas the Canon 16-35mm F2.8L III has a 82mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Sigma 18-35mm F1.8 DC HSM:
And these are the 82mm filters that we recommend for the Canon 16-35mm F2.8L III:
Lens Mounts
Both the Sigma 18-35mm F1.8 DC HSM 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 T8i, Canon 90D and Canon SL3.
Sigma 18-35mm F1.8 DC HSM is also available in Pentax KAF , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 18-35mm F1.8 DC HSM has a focal range of 18-35mm and
1.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-56mm when used on a APS-C / DX format camera.
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.