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 Nikon 18-70mm f3.5-4.5G ED-IF 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. Nikon 18-70mm f3.5-4.5G ED-IF weighs 420g, 54% (505g) lighter than the Irix 45mm F1.4's weight of 925g.
Filter Threads
The Irix 45mm F1.4 has a filter size of 77mm whereas the Nikon 18-70mm f3.5-4.5G ED-IF has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Irix 45mm F1.4:
And these are the 67mm filters that we recommend for the Nikon 18-70mm f3.5-4.5G ED-IF:
Lens Mounts
The Irix 45mm F1.4 has the Nikon F (FX) lens mount whereas the Nikon 18-70mm f3.5-4.5G ED-IF has the Nikon F (DX) lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount and Nikon D3500, Nikon D7500 and Nikon D5600 for the Nikon F (DX) Mount.
Irix 45mm F1.4 is also available in the Canon EF and Pentax KAF2 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 Nikon 18-70mm f3.5-4.5G ED-IF has a focal range of 18-70mm and 3.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-105mm when used on a APS-C / DX format camera.
