Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sigma 30mm F1.4 C is the longer of the two lenses at 73mm. The Panasonic 25mm F1.4 II ASPH with a length of 55mm is 18mm shorter. Besides being longer, the Sigma 30mm F1.4 C also has a larger diameter of 65mm compared to Panasonic 25mm F1.4 II ASPH's 63mm diameter.
Below you can find the scaled side by side image of Panasonic 25mm F1.4 II ASPH and Sigma 30mm F1.4 C to get a better idea of how their size compare in real life.
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. Panasonic 25mm F1.4 II ASPH weighs 205g, which means it is 60g (22%) lighter than the Sigma 30mm F1.4 C which has a weight of 265g.
Both Panasonic 25mm F1.4 II ASPH and Sigma 30mm F1.4 C has the same Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with the Micro Four Thirds lenses are Panasonic GH6, OM System OM-1 and Panasonic GH5 II.
Sigma 30mm F1.4 C is also available in Sony E and Fujifilm X mounts.
Panasonic 25mm F1.4 II ASPH is a prime lens with fixed focal lenght of 25mm which has a 35mm equivalent focal range of 50mm when used on a FourThirds format camera. Sigma 30mm F1.4 C is a prime lens with fixed focal lenght of 30mm which has a 35mm equivalent focal range of 37.5mm when used on a APS-C / DX format camera.