The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony 300mm F2.8 G SSM II and the Rokinon 85mm F1.4 for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Sony 300mm F2.8 G SSM II is the longer of the two lenses at 243mm. The Rokinon 85mm F1.4 with a length of 75mm, is 168mm shorter. Besides being longer, the Sony 300mm F2.8 G SSM II also has a larger diameter of 122mm compared to the Rokinon 85mm F1.4's 78mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Rokinon 85mm F1.4 weighs 539g, 76% (1761g) lighter than the Sony 300mm F2.8 G SSM II's weight of 2300g.
Below you can find the dimension and weight table of the Telephoto Prime Lenses in Sony Alpha Mount for size comparison purposes.
Telephoto Prime Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both the Sony 300mm F2.8 G SSM II and the Rokinon 85mm F1.4 has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A99 II, Sony A68 and Sony A77 II.
Rokinon 85mm F1.4 is also available in Canon EF , Four Thirds, Pentax KAF, Samsung NX and Nikon F (FX) mounts.
Focal Range
Sony 300mm F2.8 G SSM II is a prime lens with fixed focal lenght of 300mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 450mm.
Rokinon 85mm F1.4 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.