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 PENTAX28-105mm F3.5-5.6 WR 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. PENTAX28-105mm F3.5-5.6 WR is the longer of the two lenses at 87mm. The Pentax FA 50mm F1.4 with a length of 41mm, is 46mm shorter. Besides being longer, the PENTAX28-105mm F3.5-5.6 WR also has a larger diameter of 73mm compared to the Pentax FA 50mm F1.4'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 50mm F1.4 weighs 223g, which means it is 217g (49%) lighter than the PENTAX28-105mm F3.5-5.6 WR which has a weight of 440g.
Filter Threads
The Pentax FA 50mm F1.4 has a filter size of 49mm whereas the PENTAX28-105mm F3.5-5.6 WR has a 62mm 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 62mm filters that we recommend for the PENTAX28-105mm F3.5-5.6 WR:
Lens Mounts
The Pentax FA 50mm F1.4 has the Pentax KAF lens mount whereas the PENTAX28-105mm F3.5-5.6 WR has the Pentax KAF3 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 Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Pentax FA 50mm F1.4 is also available in the Pentax KAF mount.
Focal Range
Pentax FA 50mm F1.4 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 PENTAX28-105mm F3.5-5.6 WR has a focal range of 28-105mm and 3.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42 - 157.5mm.
