Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Tamron 100-400mm F4.5-6.3 Di VC USD is the longer of the two lenses at 199mm. The Sigma 100-400mm F5-6.3 DG OS HSM with a length of 182mm is 17mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 86mm.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Tamron 100-400mm F4.5-6.3 Di VC USD weighs 1135g, 2% (25g) lighter than the Sigma 100-400mm F5-6.3 DG OS HSM's weight of 1160g.
Below you can find the dimension and weight table of the 'Telephoto Zoom Lenses in Nikon F (FX) Mount for size comparison purposes.
Telephoto Zoom Lenses in Nikon F (FX) Mount for Size Comparison
Lens Mounts
Both Sigma 100-400mm F5-6.3 DG OS HSM and Tamron 100-400mm F4.5-6.3 Di VC USD has the same Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (FX) lenses are Nikon D6, Nikon D780 and Nikon D3500.
Sigma 100-400mm F5-6.3 DG OS HSM is also available in Sigma SA and Canon EF mounts.
Tamron 100-400mm F4.5-6.3 Di VC USD is also available in Canon EF mount.
Focal Range