The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 70-200mm F2.8 EX DG OS HSM and the Pentax 50-200mm F4-5.6 ED 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 70-200mm F2.8 EX DG OS HSM is the longer of the two lenses at 197mm. The Pentax 50-200mm F4-5.6 ED with a length of 80mm, is 117mm shorter. Besides being longer, the Sigma 70-200mm F2.8 EX DG OS HSM also has a larger diameter of 86mm compared to the Pentax 50-200mm F4-5.6 ED's 69mm 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. Pentax 50-200mm F4-5.6 ED weighs 272g, 80% (1158g) lighter than the Sigma 70-200mm F2.8 EX DG OS HSM's weight of 1430g.
Filter Threads
The Sigma 70-200mm F2.8 EX DG OS HSM has a filter size of 77mm whereas the Pentax 50-200mm F4-5.6 ED has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Sigma 70-200mm F2.8 EX DG OS HSM:
And these are the 49mm filters that we recommend for the Pentax 50-200mm F4-5.6 ED:
Lens Mounts
The Sigma 70-200mm F2.8 EX DG OS HSM has the Pentax KAF3 lens mount whereas the Pentax 50-200mm F4-5.6 ED has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Sigma 70-200mm F2.8 EX DG OS HSM is also available in the Canon EF , Nikon F (FX), Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 70-200mm F2.8 EX DG OS HSM has a focal range of 70-200mm and
2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
105 - 300mm.
On the other hand, the Pentax 50-200mm F4-5.6 ED has a focal range of 50-200mm and 4.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 75-300mm when used on a APS-C / DX format camera.
