Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Tamron 20mm F2.8 Di III OSD M1:2 is the longer of the two lenses at 64mm. The Sigma 17mm F4 DG DN C with a length of 51mm, is 13mm shorter. Besides being longer, the Tamron 20mm F2.8 Di III OSD M1:2 also has a larger diameter of 73mm compared to the Sigma 17mm F4 DG DN C's 64mm 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.
Filter Threads
The Sigma 17mm F4 DG DN C has a filter size of 55mm whereas the Tamron 20mm F2.8 Di III OSD M1:2 has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 55mm filters that we recommend you to consider for the Sigma 17mm F4 DG DN C:
And these are the 67mm filters that we recommend for the Tamron 20mm F2.8 Di III OSD M1:2:
Lens Mounts
Both the Sigma 17mm F4 DG DN C and the Tamron 20mm F2.8 Di III OSD M1:2 has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony FX5, Sony A7R VI and Sony A7 V.
Sigma 17mm F4 DG DN C is also available in the Leica L mount.
Focal Range
Sigma 17mm F4 DG DN C is a prime lens with fixed focal lenght of 17mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
25.5mm.
On the other hand, the Tamron 20mm F2.8 Di III OSD M1:2 is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 30mm.
