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 Fujifilm Fujinon MKX 18-55mm T2.9 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. Fujifilm Fujinon MKX 18-55mm T2.9 is the longer of the two lenses at 207mm. The Tamron 17-70 F2.8 Di III-A VC with a length of 119mm, is 88mm shorter. Besides being longer, the Fujifilm Fujinon MKX 18-55mm T2.9 also has a larger diameter of 87mm compared to the Tamron 17-70 F2.8 Di III-A VC's 75mm 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 17-70 F2.8 Di III-A VC weighs 525g, which means it is 555g (51%) lighter than the Fujifilm Fujinon MKX 18-55mm T2.9 which has a weight of 1080g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Fujifilm X Mount for size comparison purposes.
Standard Lenses in Fujifilm X Mount for Size Comparison
Filter Threads
The Tamron 17-70 F2.8 Di III-A VC has a filter size of 67mm whereas the Fujifilm Fujinon MKX 18-55mm T2.9 has a 82mm 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 82mm filters that we recommend for the Fujifilm Fujinon MKX 18-55mm T2.9:
Lens Mounts
Both the Tamron 17-70 F2.8 Di III-A VC and the Fujifilm Fujinon MKX 18-55mm T2.9 has the same Fujifilm X lens mount. Some of the latest released cameras that are compatible with the Fujifilm X lenses are Fujifilm X-S20, Fujifilm X-T5 and Fujifilm X-H2.
Tamron 17-70 F2.8 Di III-A VC is also available in Sony E mount.
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 Fujifilm Fujinon MKX 18-55mm T2.9 has a focal range of 18-55mm and 3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-82.5mm when used on a 35mm FF format camera.