The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 100-400mm F4.5-5.6 and the Sigma 120-400mm F4.5-5.6 DG 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. Sony FE 100-400mm F4.5-5.6 is the longer of the two lenses at 205mm. The Sigma 120-400mm F4.5-5.6 DG HSM with a length of 203mm, is 2mm shorter. Besides being longer, the Sony FE 100-400mm F4.5-5.6 also has a larger diameter of 94mm 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. Sony FE 100-400mm F4.5-5.6 weighs 1395g, which means it is 245g (14%) lighter than the Sigma 120-400mm F4.5-5.6 DG HSM which has a weight of 1640g.
Filter Threads
Both the Sony FE 100-400mm F4.5-5.6 and the Sigma 120-400mm F4.5-5.6 DG HSM have the same Filter thread size of 77mm.
Below are links to the 77mm filters that we recommend you to consider for these lenses:
Lens Mounts
The Sony FE 100-400mm F4.5-5.6 has the Sony E lens mount whereas the Sigma 120-400mm F4.5-5.6 DG HSM has the Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Sigma 120-400mm F4.5-5.6 DG HSM is also available in Sony Alpha mount.
Focal Range
Sony FE 100-400mm F4.5-5.6 has a focal range of 100-400mm 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
150 - 600mm.
On the other hand, the 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.
