The type of photography that you are planning to use is an important decision factor. Here we have evaluated the PENTAX 55-300mm F4.5-6.3 ED WR and the Sigma 70-300mm F4-5.6 DG 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 70-300mm F4-5.6 DG is the longer of the two lenses at 122mm. The PENTAX 55-300mm F4.5-6.3 ED WR with a length of 89mm, is 33mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 77mm.
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 55-300mm F4.5-6.3 ED WR weighs 471g, which means it is 79g (14%) lighter than the Sigma 70-300mm F4-5.6 DG which has a weight of 550g.
Filter Threads
Both the PENTAX 55-300mm F4.5-6.3 ED WR and the Sigma 70-300mm F4-5.6 DG have the same Filter thread size of 58mm.
Below are links to the 58mm filters that we recommend you to consider for these lenses:
Lens Mounts
The PENTAX 55-300mm F4.5-6.3 ED WR has the Pentax KAF3 lens mount whereas the Sigma 70-300mm F4-5.6 DG has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Sigma 70-300mm F4-5.6 DG is also available in Canon EF , Nikon F (FX), Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
PENTAX 55-300mm F4.5-6.3 ED WR has a focal range of 55-300mm and
5.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
82.5-450mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 70-300mm F4-5.6 DG has a focal range of 70-300mm and 4.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 450mm.