The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 20mm F2.8 Di III OSD M1:2 and the Sigma 19mm F2.8 EX DN 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 20mm F2.8 Di III OSD M1:2 is the longer of the two lenses at 64mm. The Sigma 19mm F2.8 EX DN with a length of 46mm, is 18mm 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 19mm F2.8 EX DN's 61mm 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. Sigma 19mm F2.8 EX DN weighs 140g, 36% (80g) lighter than the Tamron 20mm F2.8 Di III OSD M1:2's weight of 220g.
Filter Threads
The Tamron 20mm F2.8 Di III OSD M1:2 has a filter size of 67mm whereas the Sigma 19mm F2.8 EX DN has a 46mm 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 20mm F2.8 Di III OSD M1:2:
And these are the 46mm filters that we recommend for the Sigma 19mm F2.8 EX DN:
Lens Mounts
Both the Tamron 20mm F2.8 Di III OSD M1:2 and the Sigma 19mm F2.8 EX DN 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 19mm F2.8 EX DN is also available in Micro Four Thirds mount.
Focal Range
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.
On the other hand, the Sigma 19mm F2.8 EX DN is a prime lens with fixed focal lenght of 19mm which has an effective (full-frame 35mm equivalent) focal range of 28.5mm when used on a APS-C / DX format camera.
