The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 17-70 F2.8 Di III-A VC and the Sigma 18-35mm F1.8 DC HSM 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 18-35mm F1.8 DC HSM is the longer of the two lenses at 121mm. The Tamron 17-70 F2.8 Di III-A VC with a length of 119mm, is 2mm shorter. Besides being longer, the Sigma 18-35mm F1.8 DC HSM also has a larger diameter of 78mm compared to the Tamron 17-70 F2.8 Di III-A VC's 75mm diameter.
Below you can find a scaled side-by-side image of Tamron 17-70 F2.8 Di III-A VC and Sigma 18-35mm F1.8 DC HSM to get a better idea of how their sizes compare in real life.
Comparison image of the Tamron 17-70 F2.8 Di III-A VC and the Sigma 18-35mm F1.8 DC HSM Size and Weight 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 17-70 F2.8 Di III-A VC weighs 525g, which means it is 285g (35%) lighter than the Sigma 18-35mm F1.8 DC HSM which has a weight of 810g.
Filter Threads
The Tamron 17-70 F2.8 Di III-A VC has a filter size of 67mm whereas the Sigma 18-35mm F1.8 DC HSM has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Tamron 17-70 F2.8 Di III-A VC:
And these are the 72mm filters that we recommend for the Sigma 18-35mm F1.8 DC HSM:
Lens Mounts
The Tamron 17-70 F2.8 Di III-A VC has the Fujifilm X lens mount whereas the Sigma 18-35mm F1.8 DC HSM has the Sigma SA lens mount . Some of the latest released cameras that are compatible with these mounts are Fujifilm X-T30 III , Fujifilm X-E5 and Fujifilm X-M5 for the Fujifilm X Mount and Sigma SD1 Merrill , Sigma SD1 and
Canon EF , Pentax KAF , Sony Alpha and Nikon F (DX) mounts.
Focal Range
Tamron 17-70 F2.8 Di III-A VC has a focal range of 17-70mm and
4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
25.5-105mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 18-35mm F1.8 DC HSM has a focal range of 18-35mm and 1.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-52.5mm when used on a APS-C / DX format camera.
