The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Irix 45mm F1.4 and the Pentax smc 16-50mm F2.8 ED 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 smc 16-50mm F2.8 ED weighs 565g, 38% (360g) lighter than the Irix 45mm F1.4's weight of 925g.
Filter Threads
Both the Irix 45mm F1.4 and the Pentax smc 16-50mm F2.8 ED have the same Filter thread size of 77mm.
Below are links to the 77mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Irix 45mm F1.4 and the Pentax smc 16-50mm F2.8 ED has the same Pentax KAF2 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF2 lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Irix 45mm F1.4 is also available in the Canon EF and Nikon F (FX) mounts.
Focal Range
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.
On the other hand, the Pentax smc 16-50mm F2.8 ED has a focal range of 16-50mm and 3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 24-75mm when used on a APS-C / DX format camera.
