The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon EF-S 18-55mm F4-5.6 IS STM and the Sigma 17-50mm F2.8 EX DC OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor 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 Canon EF-S 18-55mm F4-5.6 IS STM's 67mm diameter.
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. Canon EF-S 18-55mm F4-5.6 IS STM weighs 215g, which means it is 350g (61%) lighter than the Sigma 17-50mm F2.8 EX DC OS HSM which has a weight of 565g.
Lens Mounts
Both Canon EF-S 18-55mm F4-5.6 IS STM has the Canon EF-S lens mount whereas the Sigma 17-50mm F2.8 EX DC OS HSM has the Canon EF 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-S Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF 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
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. 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.