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 OS 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. 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 OS 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 OS 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 OS HSM weighs 1640g, 7% (140g) lighter than the Sigma 150-500mm F5-6.3 DG OS HSM's weight of 1780g.
Filter Threads
The Sigma 150-500mm F5-6.3 DG OS HSM has a filter size of 86mm whereas the Sigma 120-400mm F4.5-5.6 DG OS HSM 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 86mm filters that we recommend you to consider for the Sigma 150-500mm F5-6.3 DG OS HSM:
And these are the 77mm filters that we recommend for the Sigma 120-400mm F4.5-5.6 DG OS HSM:
Lens Mounts
The Sigma 150-500mm F5-6.3 DG OS HSM has the Pentax KAF3 lens mount whereas the Sigma 120-400mm F4.5-5.6 DG OS HSM has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and Canon 1D X III, Canon 6D MII and Canon 5D MIV for the Canon EF Mount.
Sigma 150-500mm F5-6.3 DG OS HSM is also available in Canon EF , Nikon F (FX), Sony Alpha and Sigma SA mounts.
Sigma 120-400mm F4.5-5.6 DG OS HSM is also available in Sigma SA and Nikon F (FX) mounts.
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.
On the other hand, the Sigma 120-400mm F4.5-5.6 DG OS HSM has a focal range of 120-400mm and 3.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 192 - 640mm.