The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 24-70mm f2.8 VC USD and the Sigma 17-50mm F2.8 EX DC OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Tamron 24-70mm f2.8 VC USD is the longer of the two lenses at 117mm. The Sigma 17-50mm F2.8 EX DC OS HSM with a length of 92mm, is 25mm shorter. Besides being longer, the Tamron 24-70mm f2.8 VC USD also has a larger diameter of 88mm compared to the Sigma 17-50mm F2.8 EX DC OS HSM's 84mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 17-50mm F2.8 EX DC OS HSM weighs 565g, 31% (260g) lighter than the Tamron 24-70mm f2.8 VC USD's weight of 825g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Sony Alpha Mount for size comparison purposes.
Standard Zoom Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both the Tamron 24-70mm f2.8 VC USD and the Sigma 17-50mm F2.8 EX DC OS HSM has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A99 II, Sony A68 and Sony A77 II.
Tamron 24-70mm f2.8 VC USD is also available in Canon EF and Nikon F (FX) mounts.
Sigma 17-50mm F2.8 EX DC OS HSM is also available in Canon EF , Pentax KAF3, Sigma SA and Nikon F (DX) mounts.
Focal Range
Tamron 24-70mm f2.8 VC USD has a focal range of 24-70mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 36 - 105mm.
Sigma 17-50mm F2.8 EX DC OS HSM has a focal range of 17-50mm and 2.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 25.5-75mm when used on a APS-C / DX format camera.