The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Fujifilm 18-135mm F3.5-5.6 R OIS and the Samyang 20mm F1.8 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. Fujifilm 18-135mm F3.5-5.6 R OIS is the longer of the two lenses at 98mm. The Samyang 20mm F1.8 with a length of 88mm, is 10mm shorter. On the other hand, the Samyang 20mm F1.8 has a larger diameter of 83mm compared to the Fujifilm 18-135mm F3.5-5.6 R OIS's 76mm 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. Fujifilm 18-135mm F3.5-5.6 R OIS weighs 490g, which means it is 7g (1%) lighter than the Samyang 20mm F1.8 which has a weight of 497g.
Filter Threads
The Fujifilm 18-135mm F3.5-5.6 R OIS has a filter size of 67mm whereas the Samyang 20mm F1.8 has a 77mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Fujifilm 18-135mm F3.5-5.6 R OIS:
And these are the 77mm filters that we recommend for the Samyang 20mm F1.8:
Lens Mounts
Both the Fujifilm 18-135mm F3.5-5.6 R OIS and the Samyang 20mm F1.8 has the same Fujifilm X lens mount. Some of the latest released cameras that are compatible with the Fujifilm X lenses are Fujifilm X-S20, Fujifilm X-T5 and Fujifilm X-H2.
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
Fujifilm 18-135mm F3.5-5.6 R OIS has a focal range of 18-135mm and
7.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-202.5mm when used on a APS-C / DX format camera.
On the other hand, the Samyang 20mm F1.8 is a prime lens with fixed focal lenght of 20mm.