The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Nikon 18-55mm F3.5-5.6G 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. Sigma 15mm F2.8 EX DG Fisheye is the longer of the two lenses at 65mm. The Nikon 18-55mm F3.5-5.6G with a length of 63mm, is 2mm shorter. Besides being longer, the Sigma 15mm F2.8 EX DG Fisheye also has a larger diameter of 74mm compared to the Nikon 18-55mm F3.5-5.6G'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. Nikon 18-55mm F3.5-5.6G weighs 195g, which means it is 175g (47%) lighter than the Sigma 15mm F2.8 EX DG Fisheye which has a weight of 370g.
Lens Mounts
The Nikon 18-55mm F3.5-5.6G has the Nikon F (DX) lens mount whereas the Sigma 15mm F2.8 EX DG Fisheye has the Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D3500, Nikon D7500 and Nikon D5600 for the Nikon F (DX) Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Sigma 15mm F2.8 EX DG Fisheye is also available in Canon EF , Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
Nikon 18-55mm F3.5-5.6G has a focal range of 18-55mm and
3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-82.5mm when used on a APS-C / DX format camera.
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.