The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 28-70mm F2.8 DG DN and the Tamron AF 18-250mm f3.5-6.3 II 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 28-70mm F2.8 DG DN is the longer of the two lenses at 102mm. The Tamron AF 18-250mm f3.5-6.3 II LD with a length of 84mm, is 18mm shorter. On the other hand, the Tamron AF 18-250mm f3.5-6.3 II LD has a larger diameter of 74mm compared to the Sigma 28-70mm F2.8 DG DN's 72mm 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 AF 18-250mm f3.5-6.3 II LD weighs 430g, 8% (40g) lighter than the Sigma 28-70mm F2.8 DG DN's weight of 470g.
Filter Threads
The Sigma 28-70mm F2.8 DG DN has a filter size of 67mm whereas the Tamron AF 18-250mm f3.5-6.3 II LD has a 62mm 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 Sigma 28-70mm F2.8 DG DN:
And these are the 62mm filters that we recommend for the Tamron AF 18-250mm f3.5-6.3 II LD:
Lens Mounts
The Sigma 28-70mm F2.8 DG DN has the Sony E lens mount whereas the Tamron AF 18-250mm f3.5-6.3 II LD has the Sony Alpha 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 Sony A68, Sony A77 II and Sony A58 for the Sony Alpha Mount.
Tamron AF 18-250mm f3.5-6.3 II LD is also available in Canon EF , Nikon F (DX) and Pentax KAF mounts.
Focal Range
Sigma 28-70mm F2.8 DG DN has a focal range of 28-70mm and
2.5X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42 - 105mm.
On the other hand, the Tamron AF 18-250mm f3.5-6.3 II LD has a focal range of 18-250mm and 13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-375mm when used on a APS-C / DX format camera.
