The type of photography that you are planning to use is an important decision factor. Here we have evaluated the HD Pentax-DA 11-18mm F2.8 and the Sigma 12-24mm F4.5-5.6 EX DG 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 12-24mm F4.5-5.6 EX DG HSM is the longer of the two lenses at 103mm. The HD Pentax-DA 11-18mm F2.8 with a length of 100mm, is 3mm shorter. On the other hand, the HD Pentax-DA 11-18mm F2.8 has a larger diameter of 90mm compared to the Sigma 12-24mm F4.5-5.6 EX DG HSM's 87mm 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 12-24mm F4.5-5.6 EX DG HSM weighs 600g, 14% (104g) lighter than the HD Pentax-DA 11-18mm F2.8's weight of 704g.
Lens Mounts
The HD Pentax-DA 11-18mm F2.8 has the Pentax KAF3 lens mount whereas the Sigma 12-24mm F4.5-5.6 EX DG HSM has the Pentax KAF 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 KAF3 Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Sigma 12-24mm F4.5-5.6 EX DG HSM is also available in Canon EF , Sony Alpha, Sigma SA and Nikon F (FX) mounts.
Focal Range
HD Pentax-DA 11-18mm F2.8 has a focal range of 11-18mm and
1.6X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
16.5-27mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 12-24mm F4.5-5.6 EX DG HSM has a focal range of 12-24mm and 2.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 18 - 36mm.
