Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Panasonic S 50mm F1.4 is the longer of the two lenses at 130mm. The Sigma 56mm F1.4 DC DN C with a length of 60mm is 70mm shorter. Besides being longer, the Panasonic S 50mm F1.4 also has a larger diameter of 90mm compared to Sigma 56mm F1.4 DC DN C's 67mm 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 56mm F1.4 DC DN C weighs 280g, which means it is 675g (241%) lighter than the Panasonic S 50mm F1.4 which has a weight of 955g.
Both Sigma 56mm F1.4 DC DN C has the Leica L lens mount whereas the Panasonic S 50mm F1.4 has the Leica SL lens mount. Some of the latest released cameras that are compatible with these mounts are Leica TL2, Leica TL and Leica T Typ 701 for the Leica L Mount and Sigma fp L, Leica SL2-S and Panasonic S5 for the Leica SL Mount.
Sigma 56mm F1.4 DC DN C is also available in Micro Four Thirds and Sony E mounts.
Sigma 56mm F1.4 DC DN C is a prime lens with fixed focal lenght of 56mm which has a 35mm equivalent focal range of 84mm when used on a APS-C / DX format camera. Panasonic S 50mm F1.4 is a prime lens with fixed focal lenght of 50mm.