The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax FA 50mm F1.4 and the Pentax 50mm F1.8 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. Pentax 50mm F1.8 is the longer of the two lenses at 39mm. The Pentax FA 50mm F1.4 with a length of 38mm, is 1mm shorter. On the other hand, the Pentax FA 50mm F1.4 has a larger diameter of 64mm compared to the Pentax 50mm F1.8's 63mm 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 50mm F1.8 weighs 122g, 44% (98g) lighter than the Pentax FA 50mm F1.4's weight of 220g.
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 Pentax FA 50mm F1.4 has a filter size of 49mm whereas the Pentax 50mm F1.8 has a 52mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 49mm filters that we recommend you to consider for the Pentax FA 50mm F1.4:
And these are the 52mm filters that we recommend for the Pentax 50mm F1.8:
Lens Mounts
Both the Pentax FA 50mm F1.4 and the Pentax 50mm F1.8 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.
Pentax FA 50mm F1.4 is also available in Pentax KAF mount.
Focal Range
Both lenses have the same focal range of
50mm but while Pentax FA 50mm F1.4 has the fastest aperture of
F1.4, the Pentax 50mm F1.8's widest aperture value is
F1.8.