The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 15mm F2.8 EX DG Fisheye and the Pentax 12-24mm F4.0 ED AL 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. Pentax 12-24mm F4.0 ED AL is the longer of the two lenses at 84mm. The Sigma 15mm F2.8 EX DG Fisheye with a length of 65mm, is 19mm shorter. Besides being longer, the Pentax 12-24mm F4.0 ED AL also has a larger diameter of 88mm compared to the Sigma 15mm F2.8 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 15mm F2.8 EX DG Fisheye weighs 370g, which means it is 60g (13%) lighter than the Pentax 12-24mm F4.0 ED AL which has a weight of 430g.
Lens Mounts
Both the Sigma 15mm F2.8 EX DG Fisheye and the Pentax 12-24mm F4.0 ED AL has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 15mm F2.8 EX DG Fisheye is also available in the Canon EF , Nikon F (FX), Sony Alpha and Sigma SA mounts.
Focal Range
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.
On the other hand, the Pentax 12-24mm F4.0 ED AL has a focal range of 12-24mm and 2.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 18-36mm when used on a APS-C / DX format camera.
