The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 20-40mm F2.8 VXD and the Tamron 17-28mm F2.8 Di III 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 17-28mm F2.8 Di III is the longer of the two lenses at 99mm. The Tamron 20-40mm F2.8 VXD with a length of 86mm, is 13mm shorter. On the other hand, the Tamron 20-40mm F2.8 VXD has a larger diameter of 74mm compared to the Tamron 17-28mm F2.8 Di III's 73mm diameter.
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Below you can find a scaled side-by-side image of Tamron 20-40mm F2.8 VXD and Tamron 17-28mm F2.8 Di III to get a better idea of how their sizes compare in real life.
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 20-40mm F2.8 VXD weighs 365g, which means it is 55g (13%) lighter than the Tamron 17-28mm F2.8 Di III which has a weight of 420g.
Filter Threads
Both the Tamron 20-40mm F2.8 VXD and the Tamron 17-28mm F2.8 Di III 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
Both the Tamron 20-40mm F2.8 VXD and the Tamron 17-28mm F2.8 Di III has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A9 III, Sony A7C Mark II and Sony A7CR.
Focal Range
Tamron 20-40mm F2.8 VXD has a focal range of 20-40mm and
2.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30 - 60mm.
On the other hand, the Tamron 17-28mm F2.8 Di III has a focal range of 17-28mm and 1.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 25.5 - 42mm.