The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Irix 11mm F4 and the Sigma 8mm F3.5 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. Irix 11mm F4 is the longer of the two lenses at 118mm. The Sigma 8mm F3.5 EX DG Fisheye with a length of 69mm, is 49mm shorter. Besides being longer, the Irix 11mm F4 also has a larger diameter of 103mm compared to the Sigma 8mm F3.5 EX DG Fisheye's 74mm 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 8mm F3.5 EX DG Fisheye weighs 400g, 49% (390g) lighter than the Irix 11mm F4's weight of 790g.
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 Irix 11mm F4 and the Sigma 8mm F3.5 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.
Irix 11mm F4 is also available in the Canon EF and Pentax KAF3 mounts.
Sigma 8mm F3.5 EX DG Fisheye is also available in Canon EF and Sigma SA mounts.
Focal Range
Irix 11mm F4 is a prime lens with fixed focal lenght of 11mm.
On the other hand, the Sigma 8mm F3.5 EX DG Fisheye is a prime lens with fixed focal lenght of 8mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 12mm.
