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 Tamron AF 18-270mm f3.5-6.3 II VC LD 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. Tamron AF 18-270mm f3.5-6.3 II VC LD is the longer of the two lenses at 101mm. The Sigma 15mm F2.8 EX DG Fisheye with a length of 65mm, is 36mm shorter. Besides being longer, the Tamron AF 18-270mm f3.5-6.3 II VC LD also has a larger diameter of 80mm 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 190g (33%) lighter than the Tamron AF 18-270mm f3.5-6.3 II VC LD which has a weight of 560g.
Lens Mounts
Both the Sigma 15mm F2.8 EX DG Fisheye and the Tamron AF 18-270mm f3.5-6.3 II VC LD has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Sigma 15mm F2.8 EX DG Fisheye is also available in Nikon F (FX) , Pentax KAF, Sony Alpha and Sigma SA mounts.
Tamron AF 18-270mm f3.5-6.3 II VC LD is also available in Nikon F (DX) mount.
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 1.6x crop, it provides a 35mm (FF) equivalent of
24mm.
On the other hand, the Tamron AF 18-270mm f3.5-6.3 II VC LD has a focal range of 18-270mm and 15.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-432mm when used on a APS-C / DX format camera.