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 18-50mm F2.8 DC DN C 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 17-70 F2.8 Di III-A VC is the longer of the two lenses at 119mm. The Sigma 18-50mm F2.8 DC DN C with a length of 75mm, is 44mm shorter. Besides being longer, the Tamron 17-70 F2.8 Di III-A VC also has a larger diameter of 75mm compared to the Sigma 18-50mm F2.8 DC DN C's 65mm diameter.
Below you can find a scaled side-by-side image of Tamron 17-70 F2.8 Di III-A VC and Sigma 18-50mm F2.8 DC DN C 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 18-50mm F2.8 DC DN C 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. Sigma 18-50mm F2.8 DC DN C weighs 290g, 44% (235g) lighter than the Tamron 17-70 F2.8 Di III-A VC's weight of 525g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Sony E Mount for size comparison purposes.
Standard Sony E Mount
Filter Threads
The Tamron 17-70 F2.8 Di III-A VC has a filter size of 67mm whereas the Sigma 18-50mm F2.8 DC DN C has a 55mm 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 55mm filters that we recommend for the Sigma 18-50mm F2.8 DC DN C:
Lens Mounts
Both the Tamron 17-70 F2.8 Di III-A VC and the Sigma 18-50mm F2.8 DC DN C has the same Sony E lens mount . Some of the latest released cameras that are compatible with the Sony E lenses are Sony ZV-E10 II , Sony A6700 and Sony FX30 .
Leica L and Fujifilm X 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 18-50mm F2.8 DC DN C has a focal range of 18-50mm and 2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-75mm when used on a APS-C / DX format camera.
