The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 17-28mm F2.8 Di III 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. Tamron 17-28mm F2.8 Di III is the longer of the two lenses at 99mm. The Sigma 4.5mm F2.8 EX DC HSM Fisheye with a length of 78mm, is 21mm shorter. On the other hand, the Sigma 4.5mm F2.8 EX DC HSM Fisheye has a larger diameter of 76mm compared to the Tamron 17-28mm F2.8 Di III's 73mm 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. Tamron 17-28mm F2.8 Di III weighs 420g, which means it is 50g (10%) lighter than the Sigma 4.5mm F2.8 EX DC HSM Fisheye which has a weight of 470g.
Lens Mounts
The Tamron 17-28mm F2.8 Di III has the Sony E lens mount whereas the Sigma 4.5mm F2.8 EX DC HSM Fisheye has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount.
Sigma 4.5mm F2.8 EX DC HSM Fisheye is also available in Sigma SA and Nikon F (DX) mounts.
Focal Range
Tamron 17-28mm F2.8 Di III has a focal range of 17-28mm and
1.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
25.5 - 42mm.
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.
