The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 70-300mm F4-5.6 DG and the Canon 100-300mm f4.5-5.6 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 100-300mm f4.5-5.6 USM weighs 540g, 1% (10g) lighter than the Sigma 70-300mm F4-5.6 DG's weight of 550g.
Filter Threads
Both the Sigma 70-300mm F4-5.6 DG and the Canon 100-300mm f4.5-5.6 USM have the same Filter thread size of 58mm.
Below are links to the 58mm filters that we recommend you to consider for these lenses:
Lens Mounts
The Sigma 70-300mm F4-5.6 DG has the Nikon F (FX) lens mount whereas the Canon 100-300mm f4.5-5.6 USM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount and Blackmagic URSA 12K LF, Z CAM E2-F6 II 6K and Z CAM E2-S6 II 6K for the Canon EF Mount.
Sigma 70-300mm F4-5.6 DG is also available in the Canon EF , Pentax KAF, Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 70-300mm F4-5.6 DG has a focal range of 70-300mm and
4.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
105 - 450mm.
On the other hand, the Canon 100-300mm f4.5-5.6 USM has a focal range of 100-300mm and 3.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 160 - 480mm.
