The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 18-55mm F3.5-5.6 AL WR and the Pentax 40mm F2.8 L 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. Pentax 18-55mm F3.5-5.6 AL WR is the longer of the two lenses at 68mm. The Pentax 40mm F2.8 L with a length of 15mm, is 53mm shorter. Besides being longer, the Pentax 18-55mm F3.5-5.6 AL WR also has a larger diameter of 69mm compared to the Pentax 40mm F2.8 L's 63mm 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 40mm F2.8 L weighs 80g, 65% (150g) lighter than the Pentax 18-55mm F3.5-5.6 AL WR's weight of 230g.
Filter Threads
The Pentax 18-55mm F3.5-5.6 AL WR has a filter size of 52mm whereas the Pentax 40mm F2.8 L has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 52mm filters that we recommend you to consider for the Pentax 18-55mm F3.5-5.6 AL WR:
And these are the 49mm filters that we recommend for the Pentax 40mm F2.8 L:
Lens Mounts
Both the Pentax 18-55mm F3.5-5.6 AL WR and the Pentax 40mm F2.8 L has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Pentax 40mm F2.8 L is also available in Pentax KAF mount.
Focal Range
Pentax 18-55mm F3.5-5.6 AL WR has a focal range of 18-55mm and
3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-82.5mm when used on a APS-C / DX format camera.
On the other hand, the Pentax 40mm F2.8 L is a prime lens with fixed focal lenght of 40mm which has an effective (full-frame 35mm equivalent) focal range of 60mm when used on a APS-C / DX format camera.
