The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Rokinon 24mm f1.4 and the Voigtlander 20mm F3.5 SL II for their suitability to various photography scenarios:
Size and Weight Comparison
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. Voigtlander 20mm F3.5 SL II weighs 205g, 64% (375g) lighter than the Rokinon 24mm f1.4's weight of 580g.
Filter Threads
The Rokinon 24mm f1.4 has a filter size of 77mm whereas the Voigtlander 20mm F3.5 SL II has a 52mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Rokinon 24mm f1.4:
And these are the 52mm filters that we recommend for the Voigtlander 20mm F3.5 SL II:
Lens Mounts
Both the Rokinon 24mm f1.4 and the Voigtlander 20mm F3.5 SL II has the same Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (FX) lenses are Nikon D6, Nikon D780 and Nikon D3500.
Rokinon 24mm f1.4 is also available in Canon EF , Four Thirds, Pentax KAF, Sony Alpha and Samsung NX mounts.
Voigtlander 20mm F3.5 SL II is also available in Canon EF and Pentax KAF mounts.
Focal Range
Rokinon 24mm f1.4 is a prime lens with fixed focal lenght of 24mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
36mm.
On the other hand, the Voigtlander 20mm F3.5 SL II 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.