The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 300-800mm F5.6 EX DG HSM and the Canon 100-400mm f4.5-5.6L 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. Sigma 300-800mm F5.6 EX DG HSM is the longer of the two lenses at 544mm. The Canon 100-400mm f4.5-5.6L IS USM with a length of 189mm, is 355mm shorter. Besides being longer, the Sigma 300-800mm F5.6 EX DG HSM also has a larger diameter of 157mm compared to the Canon 100-400mm f4.5-5.6L IS USM's 92mm 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. Canon 100-400mm f4.5-5.6L IS USM weighs 1380g, 76% (4500g) lighter than the Sigma 300-800mm F5.6 EX DG HSM's weight of 5880g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Canon EF Mount for size comparison purposes.
Super Telephoto Lenses in Canon EF Mount for Size Comparison
Filter Threads
The Sigma 300-800mm F5.6 EX DG HSM has a filter size of 46mm whereas the Canon 100-400mm f4.5-5.6L 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 46mm filters that we recommend you to consider for the Sigma 300-800mm F5.6 EX DG HSM:
And these are the 77mm filters that we recommend for the Canon 100-400mm f4.5-5.6L IS USM:
Lens Mounts
Both the Sigma 300-800mm F5.6 EX DG HSM and the Canon 100-400mm f4.5-5.6L IS USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Sigma 300-800mm F5.6 EX DG HSM is also available in Sigma SA and Nikon F (FX) mounts.
Focal Range
Sigma 300-800mm F5.6 EX DG HSM has a focal range of 300-800mm and
2.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
480 - 1280mm.
On the other hand, the Canon 100-400mm f4.5-5.6L IS USM has a focal range of 100-400mm and 4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 160 - 640mm.