The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Rokinon 85mm F1.8 and the Samyang 300mm f6.3 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. Rokinon 85mm F1.8 is the longer of the two lenses at 81mm. The Samyang 300mm f6.3 with a length of 74mm, is 7mm shorter. Besides being longer, the Rokinon 85mm F1.8 also has a larger diameter of 68mm compared to the Samyang 300mm f6.3's 65mm 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. Samyang 300mm f6.3 weighs 318g, 7% (26g) lighter than the Rokinon 85mm F1.8's weight of 344g.
Lens Mounts
Both the Rokinon 85mm F1.8 and the Samyang 300mm f6.3 has the same Canon EF-M lens mount. Some of the latest released cameras that are compatible with the Canon EF-M lenses are Canon M50 II, Canon M200 and Canon M6 MII.
Rokinon 85mm F1.8 is also available in Fujifilm X and Sony E mounts.
Samyang 300mm f6.3 is also available in Fujifilm X , Micro Four Thirds and Sony E mounts.
Focal Range
Rokinon 85mm F1.8 is a prime lens with fixed focal lenght of 85mm which has an effective (full-frame 35mm equivalent) focal range of
136mm when used on a APS-C / DX format camera.
On the other hand, the Samyang 300mm f6.3 is a prime lens with fixed focal lenght of 300mm which has an effective (full-frame 35mm equivalent) focal range of 450mm when used on a APS-C / DX format camera.