The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Carl Zeiss Distagon T2,8/21 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. Carl Zeiss Distagon T2,8/21 is the longer of the two lenses at 109mm. The Samyang 20mm F1.8 with a length of 88mm, is 21mm shorter. Besides being longer, the Carl Zeiss Distagon T2,8/21 also has a larger diameter of 87mm 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, 17% (103g) lighter than the Carl Zeiss Distagon T2,8/21's weight of 600g.
Filter Threads
The Carl Zeiss Distagon T2,8/21 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 Carl Zeiss Distagon T2,8/21:
And these are the 77mm filters that we recommend for the Samyang 20mm F1.8:
Lens Mounts
Both the Carl Zeiss Distagon T2,8/21 and the Samyang 20mm F1.8 has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III.
Carl Zeiss Distagon T2,8/21 is also available in Canon EF and Nikon F (FX) mounts.
Samyang 20mm F1.8 is also available in Canon EF , Canon EF-M, Fujifilm X, Micro Four Thirds, Nikon F (FX), Samsung NX, Sony Alpha and Sony E mounts.
Focal Range
Carl Zeiss Distagon T2,8/21 is a prime lens with fixed focal lenght of 21mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
31.5mm.
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.