The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 50mm F1.4 GM 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. Sony FE 50mm F1.4 GM is the longer of the two lenses at 96mm. The Pentax FA 31mm F1.8 L with a length of 69mm, is 27mm shorter. Besides being longer, the Sony FE 50mm F1.4 GM also has a larger diameter of 81mm 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, 33% (171g) lighter than the Sony FE 50mm F1.4 GM's weight of 516g.
Filter Threads
The Sony FE 50mm F1.4 GM has a filter size of 67mm 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 67mm filters that we recommend you to consider for the Sony FE 50mm F1.4 GM:
And these are the 58mm filters that we recommend for the Pentax FA 31mm F1.8 L:
Lens Mounts
The Sony FE 50mm F1.4 GM has the Sony E 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 Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
Sony FE 50mm F1.4 GM is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
75mm.
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.
