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 10-18mm f4.5-5.6 IS STM 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. Sigma 10-20mm F3.5 EX DC HSM is the longer of the two lenses at 88mm. The Canon 10-18mm f4.5-5.6 IS STM with a length of 72mm, is 16mm shorter. Besides being longer, the Sigma 10-20mm F3.5 EX DC HSM also has a larger diameter of 87mm compared to the Canon 10-18mm f4.5-5.6 IS STM's 75mm diameter.
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 10-18mm f4.5-5.6 IS STM weighs 240g, 53% (280g) lighter than the Sigma 10-20mm F3.5 EX DC HSM's weight of 520g.
Filter Threads
The Sigma 10-20mm F3.5 EX DC HSM has a filter size of 82mm whereas the Canon 10-18mm f4.5-5.6 IS STM has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 82mm filters that we recommend you to consider for the Sigma 10-20mm F3.5 EX DC HSM:
And these are the 67mm filters that we recommend for the Canon 10-18mm f4.5-5.6 IS STM:
Lens Mounts
The Sigma 10-20mm F3.5 EX DC HSM has the Canon EF lens mount whereas the Canon 10-18mm f4.5-5.6 IS STM has the Canon EF-S lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount.
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.
On the other hand, the Canon 10-18mm f4.5-5.6 IS STM has a focal range of 10-18mm and 1.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 16-28.8mm when used on a APS-C / DX format camera.