The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 20mm F1.8 and the Sigma 24-35mm F2 DG HSM A 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 24-35mm F2 DG HSM A is the longer of the two lenses at 123mm. The Samyang 20mm F1.8 with a length of 88mm, is 35mm shorter. Besides being longer, the Sigma 24-35mm F2 DG HSM A also has a larger diameter of 88mm compared to the Samyang 20mm F1.8'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. Samyang 20mm F1.8 weighs 497g, which means it is 444g (47%) lighter than the Sigma 24-35mm F2 DG HSM A which has a weight of 941g.
Filter Threads
The Samyang 20mm F1.8 has a filter size of 77mm whereas the Sigma 24-35mm F2 DG HSM A 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 Samyang 20mm F1.8:
And these are the 82mm filters that we recommend for the Sigma 24-35mm F2 DG HSM A:
Lens Mounts
Both the Samyang 20mm F1.8 and the Sigma 24-35mm F2 DG HSM A has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Samyang 20mm F1.8 is also available in Canon EF-M , Fujifilm X, Micro Four Thirds, Nikon F (FX), Pentax KAF, Samsung NX, Sony Alpha and Sony E mounts.
Sigma 24-35mm F2 DG HSM A is also available in Nikon F (FX) and Sigma SA mounts.
Focal Range
Samyang 20mm F1.8 is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
32mm.
On the other hand, the Sigma 24-35mm F2 DG HSM A has a focal range of 24-35mm and 1.5X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 38.4 - 56mm.