The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Panasonic S 50mm F1.4 and the Pentax FA 31mm F1.8 L 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. Panasonic S 50mm F1.4 is the longer of the two lenses at 130mm. The Pentax FA 31mm F1.8 L with a length of 69mm, is 61mm shorter. Besides being longer, the Panasonic S 50mm F1.4 also has a larger diameter of 90mm compared to the Pentax FA 31mm F1.8 L's 65mm 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. Pentax FA 31mm F1.8 L weighs 345g, 63% (610g) lighter than the Panasonic S 50mm F1.4's weight of 955g.
Filter Threads
The Panasonic S 50mm F1.4 has a filter size of 77mm whereas the Pentax FA 31mm F1.8 L has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Panasonic S 50mm F1.4:
And these are the 58mm filters that we recommend for the Pentax FA 31mm F1.8 L:
Lens Mounts
The Panasonic S 50mm F1.4 has the Leica L lens mount whereas the Pentax FA 31mm F1.8 L has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Leica SL3-P, Panasonic S1 II and Panasonic S1 IIE for the Leica L Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
Panasonic S 50mm F1.4 is a prime lens with fixed focal lenght of 50mm.
On the other hand, the Pentax FA 31mm F1.8 L is a prime lens with fixed focal lenght of 31mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 46.5mm.
