The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tokina 10-17mm f3.5-4.5 Fisheye and the Sigma 4.5mm F2.8 EX DC HSM 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 4.5mm F2.8 EX DC HSM Fisheye is the longer of the two lenses at 78mm. The Tokina 10-17mm f3.5-4.5 Fisheye with a length of 71mm, is 7mm shorter. Besides being longer, the Sigma 4.5mm F2.8 EX DC HSM Fisheye also has a larger diameter of 76mm compared to the Tokina 10-17mm f3.5-4.5 Fisheye's 70mm 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. Tokina 10-17mm f3.5-4.5 Fisheye weighs 350g, which means it is 120g (25%) lighter than the Sigma 4.5mm F2.8 EX DC HSM Fisheye which has a weight of 470g.
Lens Mounts
Both the Tokina 10-17mm f3.5-4.5 Fisheye and the Sigma 4.5mm F2.8 EX DC HSM Fisheye has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Tokina 10-17mm f3.5-4.5 Fisheye is also available in Nikon F (DX) mount.
Sigma 4.5mm F2.8 EX DC HSM Fisheye is also available in Sigma SA and Nikon F (DX) mounts.
Focal Range
Tokina 10-17mm f3.5-4.5 Fisheye has a focal range of 10-17mm and
1.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
16-27.2mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 4.5mm F2.8 EX DC HSM Fisheye is a prime lens with fixed focal lenght of 5mm which has an effective (full-frame 35mm equivalent) focal range of 8mm when used on a APS-C / DX format camera.