The type of photography that you are planning to use is an important decision factor. Here we have evaluated the OM System 12-40mm F2.8 PRO II 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 120-400mm F4.5-5.6 DG OS HSM is the longer of the two lenses at 203mm. The OM System 12-40mm F2.8 PRO II with a length of 84mm, is 119mm shorter. Besides being longer, the Sigma 120-400mm F4.5-5.6 DG OS HSM also has a larger diameter of 92mm compared to the OM System 12-40mm F2.8 PRO II's 70mm 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. OM System 12-40mm F2.8 PRO II weighs 382g, which means it is 1258g (76%) lighter than the Sigma 120-400mm F4.5-5.6 DG OS HSM which has a weight of 1640g.
Filter Threads
The OM System 12-40mm F2.8 PRO II has a filter size of 62mm 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 62mm filters that we recommend you to consider for the OM System 12-40mm F2.8 PRO II:
And these are the 77mm filters that we recommend for the Sigma 120-400mm F4.5-5.6 DG OS HSM:
Lens Mounts
The OM System 12-40mm F2.8 PRO II has the Micro Four Thirds lens mount whereas the Sigma 120-400mm F4.5-5.6 DG OS HSM has the Sigma SA lens mount. Some of the latest released cameras that are compatible with these mounts are OM System OM-3 Astro, OM System OM-5 II and OM System OM-3 for the Micro Four Thirds Mount and Sigma Quattro, Sigma Quattro H and Sigma SD1 Merrill for the Sigma SA Mount.
Sigma 120-400mm F4.5-5.6 DG OS HSM is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
OM System 12-40mm F2.8 PRO II has a focal range of 12-40mm and
3.3X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
24-80mm when used on a FourThirds format camera.
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 .
