The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 50-500mm F4.5-6.3 DG OS HSM and the Sigma 18-200mm f3.5-6.3 II DC 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 50-500mm F4.5-6.3 DG OS HSM is the longer of the two lenses at 219mm. The Sigma 18-200mm f3.5-6.3 II DC OS HSM with a length of 88mm, is 131mm shorter. Besides being longer, the Sigma 50-500mm F4.5-6.3 DG OS HSM also has a larger diameter of 104mm compared to the Sigma 18-200mm f3.5-6.3 II DC OS HSM's 75mm 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 18-200mm f3.5-6.3 II DC OS HSM weighs 490g, 75% (1480g) lighter than the Sigma 50-500mm F4.5-6.3 DG OS HSM's weight of 1970g.
Filter Threads
The Sigma 50-500mm F4.5-6.3 DG OS HSM has a filter size of 95mm whereas the Sigma 18-200mm f3.5-6.3 II DC OS HSM has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 95mm filters that we recommend you to consider for the Sigma 50-500mm F4.5-6.3 DG OS HSM:
And these are the 62mm filters that we recommend for the Sigma 18-200mm f3.5-6.3 II DC OS HSM:
Lens Mounts
Both the Sigma 50-500mm F4.5-6.3 DG OS HSM and the Sigma 18-200mm f3.5-6.3 II DC OS HSM has the same Sigma SA lens mount. Some of the latest released cameras that are compatible with the Sigma SA lenses are Sigma Quattro, Sigma Quattro H and Sigma SD1 Merrill.
Sigma 50-500mm F4.5-6.3 DG OS HSM is also available in Canon EF , Pentax KAF3, Sony Alpha and Nikon F (FX) mounts.
Sigma 18-200mm f3.5-6.3 II DC OS HSM is also available in Canon EF and Nikon F (DX) mounts.
Focal Range
Sigma 50-500mm F4.5-6.3 DG OS HSM has a focal range of 50-500mm and
10.0X zoom ratio .
On the other hand, the Sigma 18-200mm f3.5-6.3 II DC OS HSM 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.