The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.8 EX DG RF and the Nikon Fisheye-16mm f2.8D 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. Sigma 20mm F1.8 EX DG RF is the longer of the two lenses at 90mm. The Nikon Fisheye-16mm f2.8D with a length of 57mm, is 33mm shorter. Besides being longer, the Sigma 20mm F1.8 EX DG RF also has a larger diameter of 89mm compared to the Nikon Fisheye-16mm f2.8D's 63mm 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. Nikon Fisheye-16mm f2.8D weighs 290g, 44% (230g) lighter than the Sigma 20mm F1.8 EX DG RF's weight of 520g.
Lens Mounts
The Sigma 20mm F1.8 EX DG RF has the Nikon F (DX) lens mount whereas the Nikon Fisheye-16mm f2.8D has the Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (DX) Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Sigma 20mm F1.8 EX DG RF is also available in Canon EF , Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 20mm F1.8 EX DG RF 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.
On the other hand, the Nikon Fisheye-16mm f2.8D is a prime lens with fixed focal lenght of 16mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 24mm.