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 D FA 24-70mm F2.8 ED SDM WR 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 D FA 24-70mm F2.8 ED SDM WR weighs 787g, 14% (138g) lighter than the Irix 45mm F1.4's weight of 925g.
Lens Mounts
The Irix 45mm F1.4 has the Pentax KAF2 lens mount whereas the Pentax D FA 24-70mm F2.8 ED SDM 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 KAF2 Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
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 D FA 24-70mm F2.8 ED SDM WR has a focal range of 24-70mm 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 36 - 105mm.
