The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 24mm F1.8 EX DG 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 Sigma 24mm F1.8 EX DG with a length of 83mm, is 7mm shorter. Besides being longer, the Sigma 20mm F1.8 EX DG RF also has a larger diameter of 89mm compared to the Sigma 24mm F1.8 EX DG's 84mm 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 24mm F1.8 EX DG weighs 500g, which means it is 20g (3%) lighter than the Sigma 20mm F1.8 EX DG RF which has a weight of 520g.
Filter Threads
The Sigma 24mm F1.8 EX DG 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 Sigma 24mm F1.8 EX DG:
And these are the 82mm filters that we recommend for the Sigma 20mm F1.8 EX DG RF:
Lens Mounts
The Sigma 24mm F1.8 EX DG has the Nikon F (FX) lens mount whereas the Sigma 20mm F1.8 EX DG RF has the Sigma SA lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount and Sigma Quattro, Sigma Quattro H and Sigma SD1 Merrill for the Sigma SA Mount.
Sigma 24mm F1.8 EX DG is also available in the Canon EF , Nikon F (FX), Four Thirds, Pentax KAF, Sony Alpha, Sigma SA, Canon EF, Pentax KAF, Sony Alpha and Sigma SA mounts.
Sigma 20mm F1.8 EX DG RF is also available in Canon EF , Nikon F (DX), Pentax KAF and Sony Alpha mounts.
Focal Range
Sigma 24mm F1.8 EX DG is a prime lens with fixed focal lenght of 28mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42mm.
On the other hand, the Sigma 20mm F1.8 EX DG RF is a prime lens with fixed focal lenght of 20mm.
