The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 120-400mm F4.5-5.6 DG HSM and the Pentax DA 60-250mm F4.0 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 120-400mm F4.5-5.6 DG HSM is the longer of the two lenses at 203mm. The Pentax DA 60-250mm F4.0 ED with a length of 168mm, is 35mm shorter. Besides being longer, the Sigma 120-400mm F4.5-5.6 DG HSM also has a larger diameter of 92mm compared to the Pentax DA 60-250mm F4.0 ED's 82mm 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 DA 60-250mm F4.0 ED weighs 1040g, 36% (600g) lighter than the Sigma 120-400mm F4.5-5.6 DG HSM's weight of 1640g.
Filter Threads
The Sigma 120-400mm F4.5-5.6 DG HSM has a filter size of 77mm whereas the Pentax DA 60-250mm F4.0 ED has a 67mm 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 120-400mm F4.5-5.6 DG HSM:
And these are the 67mm filters that we recommend for the Pentax DA 60-250mm F4.0 ED:
Lens Mounts
The Sigma 120-400mm F4.5-5.6 DG HSM has the Pentax KAF3 lens mount whereas the Pentax DA 60-250mm F4.0 ED has the Pentax KAF2 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 , and for the Pentax KAF2 Mount.
Sigma 120-400mm F4.5-5.6 DG HSM is also available in the Sony Alpha mount.
Focal Range
Sigma 120-400mm F4.5-5.6 DG HSM has a focal range of 120-400mm and
3.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
180 - 600mm.
On the other hand, the Pentax DA 60-250mm F4.0 ED has a focal range of 60-250mm and 4.2X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 90-375mm when used on a APS-C / DX format camera.
