The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 10-20mm F4-5.6 EX DC 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 10-20mm F4-5.6 EX DC HSM is the longer of the two lenses at 81mm. The Rokinon 8mm f3.5 Fisheye with a length of 77mm, is 4mm shorter. Besides being longer, the Sigma 10-20mm F4-5.6 EX DC HSM also has a larger diameter of 84mm 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, 5% (27g) lighter than the Sigma 10-20mm F4-5.6 EX DC HSM's weight of 470g.
Lens Mounts
Both the Sigma 10-20mm F4-5.6 EX DC HSM and the Rokinon 8mm f3.5 Fisheye has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A68, Sony A77 II and Sony A58.
Sigma 10-20mm F4-5.6 EX DC HSM is also available in the Canon EF , Four Thirds, Pentax KAF, Sigma SA and Nikon F (DX) mounts.
Rokinon 8mm f3.5 Fisheye is also available in Canon EF , Nikon F (FX), Four Thirds, Pentax KAF and Samsung NX mounts.
Focal Range
Sigma 10-20mm F4-5.6 EX DC HSM has a focal range of 10-20mm and
2.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
15-30mm when used on a APS-C / DX format camera.
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.
