The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 17-50mm F2.8 EX DC OS HSM and the Canon EF-S 18-55mm F4-5.6 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 17-50mm F2.8 EX DC OS HSM is the longer of the two lenses at 92mm. The Canon EF-S 18-55mm F4-5.6 IS STM with a length of 62mm, is 30mm shorter. Besides being longer, the Sigma 17-50mm F2.8 EX DC OS HSM also has a larger diameter of 84mm compared to the Canon EF-S 18-55mm F4-5.6 IS STM's 67mm 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 EF-S 18-55mm F4-5.6 IS STM weighs 215g, 61% (350g) lighter than the Sigma 17-50mm F2.8 EX DC OS HSM's weight of 565g.
Filter Threads
The Sigma 17-50mm F2.8 EX DC OS HSM has a filter size of 77mm whereas the Canon EF-S 18-55mm F4-5.6 IS STM has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Sigma 17-50mm F2.8 EX DC OS HSM:
And these are the 58mm filters that we recommend for the Canon EF-S 18-55mm F4-5.6 IS STM:
Lens Mounts
The Sigma 17-50mm F2.8 EX DC OS HSM has the Canon EF lens mount whereas the Canon EF-S 18-55mm F4-5.6 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 17-50mm F2.8 EX DC OS HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 17-50mm F2.8 EX DC OS HSM has a focal range of 17-50mm and
2.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27.2-80mm when used on a APS-C / DX format camera.
On the other hand, the Canon EF-S 18-55mm F4-5.6 IS STM has a focal range of 18-55mm and 3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-88mm when used on a APS-C / DX format camera.