The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony 135mm F2.8 (T4.5) STF and the Samyang 300mm f6.3 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 135mm F2.8 (T4.5) STF is the longer of the two lenses at 99mm. The Samyang 300mm f6.3 with a length of 74mm, is 25mm shorter. Besides being longer, the Sony 135mm F2.8 (T4.5) STF also has a larger diameter of 80mm compared to the Samyang 300mm f6.3's 65mm 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 300mm f6.3 weighs 318g, 56% (412g) lighter than the Sony 135mm F2.8 (T4.5) STF's weight of 730g.
Lens Mounts
The Sony 135mm F2.8 (T4.5) STF has the Sony Alpha lens mount whereas the Samyang 300mm f6.3 has the Sony E lens mount. Some of the latest released cameras that are compatible with these mounts are Sony A99 II, Sony A68 and Sony A77 II for the Sony Alpha Mount and Sony ZV-E10 II, Sony A6700 and Sony FX30 for the Sony E Mount.
Samyang 300mm f6.3 is also available in Canon EF-M , Fujifilm X and Micro Four Thirds mounts.
Focal Range
Sony 135mm F2.8 (T4.5) STF 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 300mm f6.3 is a prime lens with fixed focal lenght of 300mm which has an effective (full-frame 35mm equivalent) focal range of 450mm when used on a APS-C / DX format camera.
