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 Nikon Z 70-200 F2.8 II 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. Nikon Z 70-200 F2.8 II is the longer of the two lenses at 208mm. The Pentax FA 31mm F1.8 L with a length of 69mm, is 139mm shorter. Besides being longer, the Nikon Z 70-200 F2.8 II 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 835g (70%) lighter than the Nikon Z 70-200 F2.8 II which has a weight of 1180g.
Filter Threads
The Pentax FA 31mm F1.8 L has a filter size of 58mm whereas the Nikon Z 70-200 F2.8 II 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 Nikon Z 70-200 F2.8 II:
Lens Mounts
The Pentax FA 31mm F1.8 L has the Pentax KAF lens mount whereas the Nikon Z 70-200 F2.8 II has the Nikon Z 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 Nikon ZR, Nikon Z5 II and RED Komodo-X 6K Z for the Nikon Z 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 Nikon Z 70-200 F2.8 II has a focal range of 70-200mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 300mm.
