The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Zeiss Milvus 18mm F2.8 and the Sigma 15mm F2.8 EX DG Fisheye 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. Zeiss Milvus 18mm F2.8 is the longer of the two lenses at 93mm. The Sigma 15mm F2.8 EX DG Fisheye with a length of 65mm, is 28mm shorter. On the other hand, the Sigma 15mm F2.8 EX DG Fisheye has a larger diameter of 74mm compared to the Zeiss Milvus 18mm F2.8's 73mm 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. Sigma 15mm F2.8 EX DG Fisheye weighs 370g, 48% (351g) lighter than the Zeiss Milvus 18mm F2.8's weight of 721g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Nikon F (FX) Mount for size comparison purposes.
Ultra-Wideangle Lenses in Nikon F (FX) Mount for Size Comparison
Lens Mounts
Both the Zeiss Milvus 18mm F2.8 and the Sigma 15mm F2.8 EX DG Fisheye 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.
Zeiss Milvus 18mm F2.8 is also available in Canon EF mount.
Sigma 15mm F2.8 EX DG Fisheye is also available in Canon EF , Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Zeiss Milvus 18mm F2.8 is a prime lens with fixed focal lenght of 18mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
27mm.
On the other hand, the Sigma 15mm F2.8 EX DG Fisheye is a prime lens with fixed focal lenght of 15mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 22.5mm.