Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sony FE 85mm F1.8 is the longer of the two lenses at 82mm. The Samyang AF 75mm F1.8 FE with a length of 69mm is 13mm shorter. Besides being longer, the Sony FE 85mm F1.8 also has a larger diameter of 78mm compared to Samyang AF 75mm F1.8 FE's 65mm 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. Samyang AF 75mm F1.8 FE weighs 230g, which means it is 141g (61%) lighter than the Sony FE 85mm F1.8 which has a weight of 371g.
Both Samyang AF 75mm F1.8 FE and Sony FE 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 A7 IV, Sony ZV-E10 and Sony A1.
Samyang AF 75mm F1.8 FE is a prime lens with fixed focal lenght of 75mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 112.5mm.
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 an 35mm (FF) equivalent of 127.5mm.