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 Tamron AF 28-75mm f2.8 XR 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. Tamron 17-70 F2.8 Di III-A VC is the longer of the two lenses at 119mm. The Tamron AF 28-75mm f2.8 XR LD with a length of 92mm, is 27mm shorter. Besides being longer, the Tamron 17-70 F2.8 Di III-A VC also has a larger diameter of 75mm compared to the Tamron AF 28-75mm f2.8 XR LD's 73mm 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 28-75mm f2.8 XR LD weighs 510g, 2% (15g) lighter than the Tamron 17-70 F2.8 Di III-A VC's weight of 525g.
Filter Threads
Both the Tamron 17-70 F2.8 Di III-A VC and the Tamron AF 28-75mm f2.8 XR LD have the same Filter thread size of 67mm.
Below are links to the 67mm filters that we recommend you to consider for these lenses:
Lens Mounts
The Tamron 17-70 F2.8 Di III-A VC has the Sony E lens mount whereas the Tamron AF 28-75mm f2.8 XR LD has the Sony Alpha lens mount. Some of the latest released cameras that are compatible with these mounts are Sony A6700, Sony FX30 and Sony ZV-E10 for the Sony E Mount and Sony A99 II, Sony A68 and Sony A77 II for the Sony Alpha Mount.
Tamron 17-70 F2.8 Di III-A VC is also available in Fujifilm X mount.
Tamron AF 28-75mm f2.8 XR LD is also available in Canon EF , Nikon F (FX) and Pentax KAF 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 Tamron AF 28-75mm f2.8 XR LD has a focal range of 28-75mm and 2.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42 - 112.5mm.