The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-35mm F1.8 DC HSM and the Sigma 17-70mm F2.8-4 DC 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 18-35mm F1.8 DC HSM is the longer of the two lenses at 121mm. The Sigma 17-70mm F2.8-4 DC OS HSM with a length of 89mm, is 32mm shorter. On the other hand, the Sigma 17-70mm F2.8-4 DC OS HSM has a larger diameter of 79mm compared to the Sigma 18-35mm F1.8 DC HSM's 78mm 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 17-70mm F2.8-4 DC OS HSM weighs 520g, 35% (290g) lighter than the Sigma 18-35mm F1.8 DC HSM's weight of 810g.
Filter Threads
Both the Sigma 18-35mm F1.8 DC HSM and the Sigma 17-70mm F2.8-4 DC OS HSM have the same Filter thread size of 72mm.
Below are links to the 72mm filters that we recommend you to consider for these lenses:
Lens Mounts
The Sigma 18-35mm F1.8 DC HSM has the Pentax KAF lens mount whereas the Sigma 17-70mm F2.8-4 DC OS HSM has the Pentax KAF3 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 KAF Mount and , and for the Pentax KAF3 Mount.
Sigma 18-35mm F1.8 DC HSM is also available in the Canon EF , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Sigma 17-70mm F2.8-4 DC OS HSM is also available in Canon EF , Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 18-35mm F1.8 DC HSM has a focal range of 18-35mm and
1.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-52.5mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 17-70mm F2.8-4 DC OS HSM 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.
