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 560mm F5.6 ED AW 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. Pentax 560mm F5.6 ED AW is the longer of the two lenses at 522mm. The Sigma 120-400mm F4.5-5.6 DG HSM with a length of 203mm, is 319mm shorter. Besides being longer, the Pentax 560mm F5.6 ED AW also has a larger diameter of 130mm compared to the Sigma 120-400mm F4.5-5.6 DG HSM's 92mm 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 120-400mm F4.5-5.6 DG HSM weighs 1640g, which means it is 1400g (46%) lighter than the Pentax 560mm F5.6 ED AW which has a weight of 3040g.
Filter Threads
The Sigma 120-400mm F4.5-5.6 DG HSM has a filter size of 77mm whereas the Pentax 560mm F5.6 ED AW has a 112mm 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 112mm filters that we recommend for the Pentax 560mm F5.6 ED AW:
Lens Mounts
Both the Sigma 120-400mm F4.5-5.6 DG HSM and the Pentax 560mm F5.6 ED AW has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
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 560mm F5.6 ED AW is a prime lens with fixed focal lenght of 560mm which has an effective (full-frame 35mm equivalent) focal range of 840mm when used on a APS-C / DX format camera.
