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 Classic and the Irix 45mm F1.4 for their suitability to various photography scenarios:
Size and Weight Comparison
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 Classic weighs 216g, which means it is 709g (76%) lighter than the Irix 45mm F1.4 which has a weight of 925g.
Filter Threads
The Pentax FA 50mm F1.4 Classic has a filter size of 49mm whereas the Irix 45mm F1.4 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 49mm filters that we recommend you to consider for the Pentax FA 50mm F1.4 Classic:
And these are the 77mm filters that we recommend for the Irix 45mm F1.4:
Lens Mounts
The Pentax FA 50mm F1.4 Classic has the Pentax KAF lens mount whereas the Irix 45mm F1.4 has the Pentax KAF2 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 KAF2 Mount.
Irix 45mm F1.4 is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Pentax FA 50mm F1.4 Classic 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 Irix 45mm F1.4 is a prime lens with fixed focal lenght of 45mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 67.5mm.
