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 18-200mm F3.5-6.3 DC OS HSM C 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 18-200mm F3.5-6.3 DC OS HSM C is the longer of the two lenses at 86mm. The OM System 12-40mm F2.8 PRO II with a length of 84mm, is 2mm shorter. Besides being longer, the Sigma 18-200mm F3.5-6.3 DC OS HSM C also has a larger diameter of 71mm 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 48g (11%) lighter than the Sigma 18-200mm F3.5-6.3 DC OS HSM C which has a weight of 430g.
Filter Threads
Both the OM System 12-40mm F2.8 PRO II and the Sigma 18-200mm F3.5-6.3 DC OS HSM C have the same Filter thread size of 62mm.
Below are links to the 62mm filters that we recommend you to consider for these lenses:
Lens Mounts
The OM System 12-40mm F2.8 PRO II has the Micro Four Thirds lens mount whereas the Sigma 18-200mm F3.5-6.3 DC OS HSM C 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 SD1 Merrill, Sigma SD1 and for the Sigma SA Mount.
Sigma 18-200mm F3.5-6.3 DC OS HSM C is also available in Canon EF , Nikon F (DX), Pentax KAF3 and Sony Alpha 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 18-200mm F3.5-6.3 DC OS HSM C has a focal range of 18-200mm and 11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-300mm when used on a APS-C / DX format camera.
