The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-50mm F2.8-4.5 DC OS HSM and the Canon 17-55mm f2.8 IS USM 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 17-55mm f2.8 IS USM is the longer of the two lenses at 111mm. The Sigma 18-50mm F2.8-4.5 DC OS HSM with a length of 89mm, is 22mm shorter. Besides being longer, the Canon 17-55mm f2.8 IS USM also has a larger diameter of 84mm compared to the Sigma 18-50mm F2.8-4.5 DC OS HSM's 74mm 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. Sigma 18-50mm F2.8-4.5 DC OS HSM weighs 395g, which means it is 250g (38%) lighter than the Canon 17-55mm f2.8 IS USM which has a weight of 645g.
Filter Threads
The Sigma 18-50mm F2.8-4.5 DC OS HSM has a filter size of 67mm whereas the Canon 17-55mm f2.8 IS USM has a 77mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Sigma 18-50mm F2.8-4.5 DC OS HSM:
And these are the 77mm filters that we recommend for the Canon 17-55mm f2.8 IS USM:
Lens Mounts
The Sigma 18-50mm F2.8-4.5 DC OS HSM has the Canon EF lens mount whereas the Canon 17-55mm f2.8 IS USM 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 18-50mm F2.8-4.5 DC OS HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 18-50mm F2.8-4.5 DC OS HSM has a focal range of 18-50mm and
2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-80mm when used on a APS-C / DX format camera.
On the other hand, the Canon 17-55mm f2.8 IS USM has a focal range of 17-55mm and 3.2X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-88mm when used on a APS-C / DX format camera.