The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony DT 11-18mm F4.5-5.6 and the Sigma 20mm F1.8 EX DG RF 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. Sigma 20mm F1.8 EX DG RF is the longer of the two lenses at 90mm. The Sony DT 11-18mm F4.5-5.6 with a length of 81mm, is 9mm shorter. Besides being longer, the Sigma 20mm F1.8 EX DG RF also has a larger diameter of 89mm compared to the Sony DT 11-18mm F4.5-5.6's 83mm 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. Sony DT 11-18mm F4.5-5.6 weighs 360g, which means it is 160g (30%) lighter than the Sigma 20mm F1.8 EX DG RF which has a weight of 520g.
Filter Threads
The Sony DT 11-18mm F4.5-5.6 has a filter size of 77mm whereas the Sigma 20mm F1.8 EX DG RF 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 77mm filters that we recommend you to consider for the Sony DT 11-18mm F4.5-5.6:
And these are the 82mm filters that we recommend for the Sigma 20mm F1.8 EX DG RF:
Lens Mounts
Both the Sony DT 11-18mm F4.5-5.6 and the Sigma 20mm F1.8 EX DG RF has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A68, Sony A77 II and Sony A58.
Sigma 20mm F1.8 EX DG RF is also available in Canon EF , Nikon F (DX), Pentax KAF and Sigma SA mounts.
Focal Range
Sony DT 11-18mm F4.5-5.6 has a focal range of 11-18mm and
1.6X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
16.5-27mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 20mm F1.8 EX DG RF 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.
