The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Leica SL 50mm f2 ASPH and the Sigma 40mm 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 40mm F1.4 DG HSM A is the longer of the two lenses at 131mm. The Leica SL 50mm f2 ASPH with a length of 83mm, is 48mm shorter. Besides being longer, the Sigma 40mm F1.4 DG HSM A also has a larger diameter of 88mm compared to the Leica SL 50mm f2 ASPH's 75mm 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.
Below you can find the dimension and weight table of the Standard Prime Lenses in Leica L Mount for size comparison purposes.
Standard Lenses in Leica L Mount for Size Comparison
Filter Threads
The Leica SL 50mm f2 ASPH has a filter size of 67mm whereas the Sigma 40mm F1.4 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 67mm filters that we recommend you to consider for the Leica SL 50mm f2 ASPH:
And these are the 82mm filters that we recommend for the Sigma 40mm F1.4 DG HSM A:
Lens Mounts
Both the Leica SL 50mm f2 ASPH and the Sigma 40mm 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 40mm F1.4 DG HSM A is also available in Canon EF , Nikon F (FX), Sigma SA and Sony E mounts.
Focal Range
Leica SL 50mm f2 ASPH is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
75mm.
On the other hand, the Sigma 40mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 40mm.