The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 17-70mm F4.0 AL SDM and the Sigma 24-105mm F4 DG OS HSM 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 24-105mm F4 DG OS HSM is the longer of the two lenses at 109mm. The Pentax 17-70mm F4.0 AL SDM with a length of 94mm, is 15mm shorter. Besides being longer, the Sigma 24-105mm F4 DG OS HSM also has a larger diameter of 89mm compared to the Pentax 17-70mm F4.0 AL SDM's 75mm 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 17-70mm F4.0 AL SDM weighs 485g, which means it is 400g (45%) lighter than the Sigma 24-105mm F4 DG OS HSM which has a weight of 885g.
Filter Threads
The Pentax 17-70mm F4.0 AL SDM has a filter size of 67mm whereas the Sigma 24-105mm F4 DG OS HSM has a 82mm 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 17-70mm F4.0 AL SDM:
And these are the 82mm filters that we recommend for the Sigma 24-105mm F4 DG OS HSM:
Lens Mounts
The Pentax 17-70mm F4.0 AL SDM has the Pentax KAF3 lens mount whereas the Sigma 24-105mm F4 DG OS HSM has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are , and for the Pentax KAF3 Mount and Sony A99 II, Sony A68 and Sony A77 II for the Sony Alpha Mount.
Sigma 24-105mm F4 DG OS HSM is also available in Canon EF , Nikon F (FX) and Sigma SA mounts.
Focal Range
Pentax 17-70mm F4.0 AL SDM has a focal range of 17-70mm and
4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
25.5-105mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 24-105mm F4 DG OS HSM has a focal range of 24-105mm and 4.4X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 36 - 157.5mm.
