The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 17-40mm f1.8 and the Fujifilm XF 18-120mm F4 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 XF 18-120mm F4 is the longer of the two lenses at 124mm. The Sigma 17-40mm f1.8 with a length of 116mm, is 8mm shorter. Besides being longer, the Fujifilm XF 18-120mm F4 also has a larger diameter of 77mm compared to the Sigma 17-40mm f1.8'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. Fujifilm XF 18-120mm F4 weighs 460g, 14% (75g) lighter than the Sigma 17-40mm f1.8's weight of 535g.
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 Sigma 17-40mm f1.8 has a filter size of 67mm whereas the Fujifilm XF 18-120mm F4 has a 72mm 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 17-40mm f1.8:
And these are the 72mm filters that we recommend for the Fujifilm XF 18-120mm F4:
Lens Mounts
Both the Sigma 17-40mm f1.8 and the Fujifilm XF 18-120mm F4 has the same Fujifilm X lens mount. Some of the latest released cameras that are compatible with the Fujifilm X lenses are Fujifilm X-T30 III, Fujifilm X-E5 and Fujifilm X-M5.
Sigma 17-40mm f1.8 is also available in the Sony E , Leica L and Canon RF mounts.
Focal Range
Sigma 17-40mm f1.8 has a focal range of 17-40mm and
2.4X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
25.5-60mm when used on a APS-C / DX format camera.
On the other hand, the Fujifilm XF 18-120mm F4 has a focal range of 18-120mm and 6.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-180mm when used on a APS-C / DX format camera.
