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 17-85mm f4-5.6 IS USM for their suitability to various photography scenarios:
Size and Weight Comparison
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 17-85mm f4-5.6 IS USM weighs 475g, 15% (90g) 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 17-85mm f4-5.6 IS USM 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 77mm filters that we recommend you to consider for the Sigma 17-50mm F2.8 EX DC OS HSM:
And these are the 67mm filters that we recommend for the Canon 17-85mm f4-5.6 IS USM:
Lens Mounts
The Sigma 17-50mm F2.8 EX DC OS HSM has the Canon EF lens mount whereas the Canon 17-85mm f4-5.6 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 17-50mm F2.8 EX DC OS HSM is also available in the 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 17-85mm f4-5.6 IS USM has a focal range of 17-85mm and 5.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-136mm when used on a APS-C / DX format camera.
