The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang AF 18mm F2.8 FE and the Samyang 20mm 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.Samyang 20mm F1.8 is the longer of the two lenses at 88mm. The Samyang AF 18mm F2.8 FE with a length of 61mm is 27mm shorter. Besides being longer, the Samyang 20mm F1.8 also has a larger diameter of 83mm compared to Samyang AF 18mm F2.8 FE'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. Samyang AF 18mm F2.8 FE weighs 145g, which means it is 352g (70%) lighter than the Samyang 20mm F1.8 which has a weight of 497g.
Below you can find the dimension and weight table of the 'Wideangle Prime Lenses in Sony E Mount for size comparison purposes.
Wideangle Prime Lenses in Sony E Mount for Size Comparison
Both Samyang AF 18mm F2.8 FE and Samyang 20mm 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 A7R V, Sony FX30 and Sony A7 IV.
Samyang 20mm F1.8 is also available in Canon EF , Canon EF-M, Fujifilm X, Micro Four Thirds, Nikon F (FX), Pentax KAF, Samsung NX and Sony Alpha mounts.
Samyang AF 18mm F2.8 FE is a prime lens with fixed focal lenght of 18mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 27mm.
Samyang 20mm F1.8 is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 30mm.