The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 120-400mm F4.5-5.6 DG HSM and the Tamron 150-600mm F5-6.3 Di VC USD G2 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. Tamron 150-600mm F5-6.3 Di VC USD G2 is the longer of the two lenses at 258mm. The Sigma 120-400mm F4.5-5.6 DG HSM with a length of 203mm, is 55mm shorter. Besides being longer, the Tamron 150-600mm F5-6.3 Di VC USD G2 also has a larger diameter of 106mm compared to the Sigma 120-400mm F4.5-5.6 DG HSM'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. Sigma 120-400mm F4.5-5.6 DG HSM weighs 1640g, which means it is 370g (18%) lighter than the Tamron 150-600mm F5-6.3 Di VC USD G2 which has a weight of 2010g.
Filter Threads
The Sigma 120-400mm F4.5-5.6 DG HSM has a filter size of 77mm whereas the Tamron 150-600mm F5-6.3 Di VC USD G2 has a 95mm 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 120-400mm F4.5-5.6 DG HSM:
And these are the 95mm filters that we recommend for the Tamron 150-600mm F5-6.3 Di VC USD G2:
Lens Mounts
The Sigma 120-400mm F4.5-5.6 DG HSM has the Pentax KAF3 lens mount whereas the Tamron 150-600mm F5-6.3 Di VC USD G2 has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and Sony A99 II, Sony A68 and Sony A77 II for the Sony Alpha Mount.
Sigma 120-400mm F4.5-5.6 DG HSM is also available in the Sony Alpha mount.
Tamron 150-600mm F5-6.3 Di VC USD G2 is also available in Nikon F (FX) and Canon EF mounts.
Focal Range
Sigma 120-400mm F4.5-5.6 DG HSM has a focal range of 120-400mm and
3.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
180 - 600mm.
On the other hand, the Tamron 150-600mm F5-6.3 Di VC USD G2 has a focal range of 150-600mm and 4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 225 - 900mm.