The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Leica APO-SL 28mm F2 ASPH and the Sigma 20mm F1.4 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 20mm F1.4 DG HSM A is the longer of the two lenses at 130mm. The Leica APO-SL 28mm F2 ASPH with a length of 102mm, is 28mm shorter. Besides being longer, the Sigma 20mm F1.4 DG HSM A also has a larger diameter of 91mm compared to the Leica APO-SL 28mm F2 ASPH's 73mm diameter.
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Below you can find a scaled side-by-side image of Leica APO-SL 28mm F2 ASPH and Sigma 20mm F1.4 DG HSM A to get a better idea of how their sizes compare in real life.
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. Leica APO-SL 28mm F2 ASPH weighs 700g, which means it is 250g (26%) lighter than the Sigma 20mm F1.4 DG HSM A which has a weight of 950g.
Lens Mounts
Both the Leica APO-SL 28mm F2 ASPH and the Sigma 20mm F1.4 DG HSM A has the same Leica L lens mount. Some of the latest released cameras that are compatible with the Leica L lenses are Leica SL3, Panasonic S5 II and Panasonic S5 II X.
Sigma 20mm F1.4 DG HSM A is also available in Canon EF , Nikon F (FX) and Sigma SA mounts.
Focal Range
Leica APO-SL 28mm F2 ASPH is a prime lens with fixed focal lenght of 28mm.
On the other hand, the Sigma 20mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 20mm.