The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Panasonic S 85mm F1.8 and the Sigma 105mm 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 105mm F1.4 DG HSM A is the longer of the two lenses at 132mm. The Panasonic S 85mm F1.8 with a length of 82mm, is 50mm shorter. Besides being longer, the Sigma 105mm F1.4 DG HSM A also has a larger diameter of 116mm compared to the Panasonic S 85mm F1.8's 74mm 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. Panasonic S 85mm F1.8 weighs 355g, which means it is 1290g (78%) lighter than the Sigma 105mm F1.4 DG HSM A which has a weight of 1645g.
Below you can find the dimension and weight table of the Telephoto Prime Lenses in Leica L Mount for size comparison purposes.
Telephoto Lenses in Leica L Mount for Size Comparison
Filter Threads
The Panasonic S 85mm F1.8 has a filter size of 67mm whereas the Sigma 105mm F1.4 DG HSM A has a 105mm 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 Panasonic S 85mm F1.8:
And these are the 105mm filters that we recommend for the Sigma 105mm F1.4 DG HSM A:
Lens Mounts
Both the Panasonic S 85mm F1.8 and the Sigma 105mm 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.
Focal Range
Panasonic S 85mm F1.8 is a prime lens with fixed focal lenght of 85mm.
On the other hand, the Sigma 105mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 105mm.