The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 85mm F1.8 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. Sony FE 85mm F1.8 is the longer of the two lenses at 82mm. The Rokinon 8mm f3.5 Fisheye with a length of 77mm, is 5mm shorter. Besides being longer, the Sony FE 85mm F1.8 also has a larger diameter of 78mm 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. Sony FE 85mm F1.8 weighs 371g, which means it is 72g (16%) lighter than the Rokinon 8mm f3.5 Fisheye which has a weight of 443g.
Lens Mounts
The Sony FE 85mm F1.8 has the Sony E lens mount whereas the Rokinon 8mm f3.5 Fisheye has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Sony A68, Sony A77 II and Sony A58 for the Sony Alpha Mount.
Rokinon 8mm f3.5 Fisheye is also available in Canon EF , Nikon F (FX), Four Thirds, Pentax KAF and Samsung NX mounts.
Focal Range
Sony FE 85mm F1.8 is a prime lens with fixed focal lenght of 85mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
127.5mm.
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.
