The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 90mm F2.8 DG DN C and the Rokinon 85mm F1.8 for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Rokinon 85mm F1.8 is the longer of the two lenses at 81mm. The Sigma 90mm F2.8 DG DN C with a length of 60mm is 21mm shorter. Besides being longer, the Rokinon 85mm F1.8 also has a larger diameter of 68mm compared to Sigma 90mm F2.8 DG DN C's 64mm diameter.
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. Sigma 90mm F2.8 DG DN C weighs 295g, which means it is 49g (14%) lighter than the Rokinon 85mm F1.8 which has a weight of 344g.
Below you can find the dimension and weight table of the 'Telephoto Prime Lenses in Sony E Mount for size comparison purposes.
Telephoto Prime Lenses in Sony E Mount for Size Comparison
Both Sigma 90mm F2.8 DG DN C and Rokinon 85mm F1.8 has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony FX30, Sony ZV-E10 and Sony A6600.
Sigma 90mm F2.8 DG DN C is also available in Leica L mount.
Rokinon 85mm F1.8 is also available in Canon EF-M and Fujifilm X mounts.
Sigma 90mm F2.8 DG DN C is a prime lens with fixed focal lenght of 90mm which has a 35mm equivalent focal range of 135mm when used on a 35mm FF format camera. Rokinon 85mm F1.8 is a prime lens with fixed focal lenght of 85mm which has a 35mm equivalent focal range of 135mm when used on a APS-C / DX format camera.