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 Rokinon 8mm f3.5 Fisheye 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 Rokinon 8mm f3.5 Fisheye with a length of 77mm, is 26mm 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 Rokinon 8mm f3.5 Fisheye'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. Rokinon 8mm f3.5 Fisheye weighs 443g, 26% (157g) lighter than the Sigma 12-24mm F4.5-5.6 EX DG HSM's weight of 600g.
Lens Mounts
Both the Sigma 12-24mm F4.5-5.6 EX DG HSM and the Rokinon 8mm f3.5 Fisheye has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 12-24mm F4.5-5.6 EX DG HSM is also available in the Canon EF , Sony Alpha, Sigma SA and Nikon F (FX) mounts.
Rokinon 8mm f3.5 Fisheye is also available in Canon EF , Nikon F (FX), Four Thirds, Sony Alpha and Samsung NX mounts.
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 Rokinon 8mm f3.5 Fisheye is a prime lens with fixed focal lenght of 8mm which has an effective (full-frame 35mm equivalent) focal range of 12mm when used on a APS-C / DX format camera.
