The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 50mm F1.4 AS UMC and the Pentax FA 43mm F1.9 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. Samyang 50mm F1.4 AS UMC is the longer of the two lenses at 75mm. The Pentax FA 43mm F1.9 L with a length of 27mm, is 48mm shorter. Besides being longer, the Samyang 50mm F1.4 AS UMC also has a larger diameter of 82mm compared to the Pentax FA 43mm F1.9 L's 64mm 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 43mm F1.9 L weighs 155g, 71% (380g) lighter than the Samyang 50mm F1.4 AS UMC's weight of 535g.
Below you can find the dimension and weight table of the Standard Prime Lenses in Pentax KAF Mount for size comparison purposes.
Standard Lenses in Pentax KAF Mount for Size Comparison
Filter Threads
The Samyang 50mm F1.4 AS UMC has a filter size of 77mm whereas the Pentax FA 43mm F1.9 L has a 49mm 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 Samyang 50mm F1.4 AS UMC:
And these are the 49mm filters that we recommend for the Pentax FA 43mm F1.9 L:
Lens Mounts
Both the Samyang 50mm F1.4 AS UMC and the Pentax FA 43mm F1.9 L has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III.
Samyang 50mm F1.4 AS UMC is also available in Canon EF , Nikon F (FX), Sony Alpha and Sony E mounts.
Focal Range
Samyang 50mm F1.4 AS UMC 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 43mm F1.9 L is a prime lens with fixed focal lenght of 43mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 64.5mm.