Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Sigma 17mm F4 DG DN C is the longer of the two lenses at 49mm. The Leica Summicron-T 23mm f2 ASPH with a length of 37mm, is 12mm shorter. Besides being longer, the Sigma 17mm F4 DG DN C also has a larger diameter of 64mm compared to the Leica Summicron-T 23mm f2 ASPH's 63mm 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. Leica Summicron-T 23mm f2 ASPH weighs 154g, 31% (71g) lighter than the Sigma 17mm F4 DG DN C's weight of 225g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Leica L Mount for size comparison purposes.
Wideangle Lenses in Leica L Mount for Size Comparison
Filter Threads
The Sigma 17mm F4 DG DN C has a filter size of 55mm whereas the Leica Summicron-T 23mm f2 ASPH has a 52mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 55mm filters that we recommend you to consider for the Sigma 17mm F4 DG DN C:
And these are the 52mm filters that we recommend for the Leica Summicron-T 23mm f2 ASPH:
Lens Mounts
Both the Sigma 17mm F4 DG DN C and the Leica Summicron-T 23mm f2 ASPH has the same Leica L lens mount. Some of the latest released cameras that are compatible with the Leica L lenses are Leica SL3-P, Panasonic S1 II and Panasonic S1 IIE.
Sigma 17mm F4 DG DN C is also available in the Sony E mount.
Focal Range
Sigma 17mm F4 DG DN C is a prime lens with fixed focal lenght of 17mm.
On the other hand, the Leica Summicron-T 23mm f2 ASPH is a prime lens with fixed focal lenght of 23mm which has an effective (full-frame 35mm equivalent) focal range of 34.5mm when used on a APS-C / DX format camera.
