The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 12-24mm F4.5-5.6 EX DG HSM and the Carl Zeiss Touit 2.8/12 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 Carl Zeiss Touit 2.8/12 with a length of 86mm, is 17mm shorter. Besides being longer, the Sigma 12-24mm F4.5-5.6 EX DG HSM also has a larger diameter of 87mm compared to the Carl Zeiss Touit 2.8/12's 82mm 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. Carl Zeiss Touit 2.8/12 weighs 270g, 55% (330g) lighter than the Sigma 12-24mm F4.5-5.6 EX DG HSM's weight of 600g.
Lens Mounts
The Sigma 12-24mm F4.5-5.6 EX DG HSM has the Pentax KAF lens mount whereas the Carl Zeiss Touit 2.8/12 has the Sony E 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 KAF Mount and Sony A6700, Sony FX30 and Sony ZV-E10 for the Sony E 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.
Carl Zeiss Touit 2.8/12 is also available in Fujifilm X mount.
Focal Range
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.
On the other hand, the Carl Zeiss Touit 2.8/12 is a prime lens with fixed focal lenght of 12mm which has an effective (full-frame 35mm equivalent) focal range of 18mm when used on a APS-C / DX format camera.