Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Leica APO-Summicron-SL 35mm F2 ASPH is the longer of the two lenses at 102mm. The Sigma 35mm F1.4 DG HSM with a length of 94mm is 8mm shorter. On the other hand, the Sigma 35mm F1.4 DG HSM has a larger diameter of 77mm compared to Leica APO-Summicron-SL 35mm F2 ASPH's 73mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 35mm F1.4 DG HSM weighs 665g, 7% (55g) lighter than the Leica APO-Summicron-SL 35mm F2 ASPH's weight of 720g.
Both Leica APO-Summicron-SL 35mm F2 ASPH has the Leica SL lens mount whereas the Sigma 35mm F1.4 DG HSM has the Leica L lens mount. Some of the latest released cameras that are compatible with these mounts are Sigma fp L, Leica SL2-S and Panasonic S5 for the Leica SL Mount and Sigma fp L, Leica SL2-S and Panasonic S5 for the Leica L Mount.
Sigma 35mm F1.4 DG HSM is also available in Canon EF , Pentax KAF3, Sony Alpha, Sigma SA and Nikon F (FX) mounts.