The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 20mm F1.8 and the Fujifilm 18mm F2 R 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 Fujifilm 18mm F2 R with a length of 41mm is 47mm shorter. Besides being longer, the Samyang 20mm F1.8 also has a larger diameter of 83mm compared to Fujifilm 18mm F2 R'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. Fujifilm 18mm F2 R weighs 116g, 76% (381g) lighter than the Samyang 20mm F1.8's weight of 497g.
Below you can find the dimension and weight table of the 'Wideangle Prime Lenses in Fujifilm X Mount for size comparison purposes.
Wideangle Prime Lenses in Fujifilm X Mount for Size Comparison
Lens Mounts
Both Samyang 20mm F1.8 and Fujifilm 18mm F2 R has the same Fujifilm X lens mount. Some of the latest released cameras that are compatible with the Fujifilm X lenses are Fujifilm X-T5, Fujifilm X-H2 and Fujifilm X-H2S.
Samyang 20mm F1.8 is also available in Canon EF , Canon EF-M, Micro Four Thirds, Nikon F (FX), Pentax KAF, Samsung NX, Sony Alpha and Sony E mounts.
Focal Range
Samyang 20mm F1.8 is a prime lens with fixed focal lenght of 20mm. Fujifilm 18mm F2 R is a prime lens with fixed focal lenght of 18mm which has an effective (full-frame 35mm equivalent) focal range of 27mm when used on a APS-C / DX format camera.