The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax FA 70-210mm F4 ED SDM 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. Pentax FA 70-210mm F4 ED SDM WR is the longer of the two lenses at 175mm. The Sigma 70-300mm F4-5.6 DG with a length of 122mm, is 53mm shorter. Besides being longer, the Pentax FA 70-210mm F4 ED SDM WR also has a larger diameter of 79mm compared to the Sigma 70-300mm F4-5.6 DG's 77mm 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 70-300mm F4-5.6 DG weighs 550g, 32% (269g) lighter than the Pentax FA 70-210mm F4 ED SDM WR's weight of 819g.
Filter Threads
The Pentax FA 70-210mm F4 ED SDM WR has a filter size of 67mm whereas the Sigma 70-300mm F4-5.6 DG has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Pentax FA 70-210mm F4 ED SDM WR:
And these are the 58mm filters that we recommend for the Sigma 70-300mm F4-5.6 DG:
Lens Mounts
The Pentax FA 70-210mm F4 ED SDM WR has the Pentax KAF4 lens mount whereas the Sigma 70-300mm F4-5.6 DG has the Nikon F (FX) 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 KAF4 Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Sigma 70-300mm F4-5.6 DG is also available in Canon EF , Pentax KAF, Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Pentax FA 70-210mm F4 ED SDM WR has a focal range of 70-210mm and
3.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
105-315mm 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.
