The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 150-500mm F5-6.3 DG OS HSM 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 an important deciding factor when comparing two lenses. Sigma 150-500mm F5-6.3 DG OS HSM is the longer of the two lenses at 252mm. The Sigma 120-400mm F4.5-5.6 DG HSM with a length of 203mm, is 49mm shorter. Besides being longer, the Sigma 150-500mm F5-6.3 DG OS HSM also has a larger diameter of 95mm compared to the Sigma 120-400mm F4.5-5.6 DG HSM's 92mm diameter.
The 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. Sigma 120-400mm F4.5-5.6 DG HSM weighs 1640g, 7% (140g) lighter than the Sigma 150-500mm F5-6.3 DG OS HSM's weight of 1780g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Sony Alpha Mount for size comparison purposes.
Telephoto Zoom Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both the Sigma 150-500mm F5-6.3 DG OS HSM and the Sigma 120-400mm F4.5-5.6 DG HSM has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A99 II, Sony A68 and Sony A77 II.
Sigma 150-500mm F5-6.3 DG OS HSM is also available in Canon EF , Nikon F (FX), Pentax KAF3 and Sigma SA mounts.
Sigma 120-400mm F4.5-5.6 DG HSM is also available in Pentax KAF3 mount.
Focal Range
Sigma 150-500mm F5-6.3 DG OS HSM has a focal range of 150-500mm 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 225 - 750mm.
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.