The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax FA 31mm F1.8 L and the Canon RF 50mm F1.2L USM 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. Canon RF 50mm F1.2L USM is the longer of the two lenses at 108mm. The Pentax FA 31mm F1.8 L with a length of 69mm, is 39mm shorter. Besides being longer, the Canon RF 50mm F1.2L USM 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, which means it is 605g (63%) lighter than the Canon RF 50mm F1.2L USM which has a weight of 950g.
Filter Threads
The Pentax FA 31mm F1.8 L has a filter size of 58mm whereas the Canon RF 50mm F1.2L USM has a 77mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the Pentax FA 31mm F1.8 L:
And these are the 77mm filters that we recommend for the Canon RF 50mm F1.2L USM:
Lens Mounts
The Pentax FA 31mm F1.8 L has the Pentax KAF lens mount whereas the Canon RF 50mm F1.2L USM has the Canon RF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount and Canon R6 V, Canon R6 III and Canon C50 for the Canon RF Mount.
Focal Range
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.
On the other hand, the Canon RF 50mm F1.2L USM is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 80mm.
