The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 17-85mm f4-5.6 IS USM and the Sigma 17-70mm F2.8-4 DC OS HSM 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 17-85mm f4-5.6 IS USM is the longer of the two lenses at 92mm. The Sigma 17-70mm F2.8-4 DC OS HSM with a length of 89mm, is 3mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 79mm.
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, which means it is 45g (8%) lighter than the Sigma 17-70mm F2.8-4 DC OS HSM which has a weight of 520g.
Filter Threads
The Canon 17-85mm f4-5.6 IS USM has a filter size of 67mm whereas the Sigma 17-70mm F2.8-4 DC OS HSM has a 72mm 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 Canon 17-85mm f4-5.6 IS USM:
And these are the 72mm filters that we recommend for the Sigma 17-70mm F2.8-4 DC OS HSM:
Lens Mounts
The Canon 17-85mm f4-5.6 IS USM has the Canon EF-S lens mount whereas the Sigma 17-70mm F2.8-4 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 17-70mm F2.8-4 DC OS HSM is also available in Pentax KAF3 , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
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.
On the other hand, the Sigma 17-70mm F2.8-4 DC OS HSM has a focal range of 17-70mm and 4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-112mm when used on a APS-C / DX format camera.