The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.4 DG HSM A and the Tamron 17-35mm f2.8-4 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. Sigma 20mm F1.4 DG HSM A is the longer of the two lenses at 130mm. The Tamron 17-35mm f2.8-4 LD with a length of 87mm, is 43mm shorter. Besides being longer, the Sigma 20mm F1.4 DG HSM A also has a larger diameter of 91mm compared to the Tamron 17-35mm f2.8-4 LD's 83mm 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 17-35mm f2.8-4 LD weighs 440g, 53% (510g) lighter than the Sigma 20mm F1.4 DG HSM A's weight of 950g.
Lens Mounts
Both the Sigma 20mm F1.4 DG HSM A and the Tamron 17-35mm f2.8-4 LD 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.
Sigma 20mm F1.4 DG HSM A is also available in Canon EF , Sigma SA and Leica L mounts.
Tamron 17-35mm f2.8-4 LD is also available in Canon EF mount.
Focal Range
Sigma 20mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30mm.
On the other hand, the Tamron 17-35mm f2.8-4 LD has a focal range of 17-35mm and 2.1X 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 - 52.5mm.