The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 135mm F1.8 GM 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. Sony FE 135mm F1.8 GM is the longer of the two lenses at 127mm. The Samyang 20mm F1.8 with a length of 88mm, is 39mm shorter. Besides being longer, the Sony FE 135mm F1.8 GM also has a larger diameter of 90mm compared to the Samyang 20mm F1.8's 83mm 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. Samyang 20mm F1.8 weighs 497g, 47% (453g) lighter than the Sony FE 135mm F1.8 GM's weight of 950g.
Filter Threads
The Sony FE 135mm F1.8 GM has a filter size of 82mm 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 82mm filters that we recommend you to consider for the Sony FE 135mm F1.8 GM:
And these are the 77mm filters that we recommend for the Samyang 20mm F1.8:
Lens Mounts
The Sony FE 135mm F1.8 GM has the Sony E lens mount whereas the Samyang 20mm F1.8 has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Sony A99 II, Sony A68 and Sony A77 II for the Sony Alpha Mount.
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 E mounts.
Focal Range
Sony FE 135mm F1.8 GM is a prime lens with fixed focal lenght of 135mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
202.5mm.
On the other hand, the 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 a 35mm (FF) equivalent of 30mm.
