The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax DA 18-50mm F4.5-5.6 DC WR RE 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 DA 18-50mm F4.5-5.6 DC WR RE is the longer of the two lenses at 71mm. The Pentax 40mm F2.8 L with a length of 15mm, is 56mm shorter. On the other hand, the Pentax 40mm F2.8 L has a larger diameter of 63mm compared to the Pentax DA 18-50mm F4.5-5.6 DC WR RE's 41mm 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, 49% (78g) lighter than the Pentax DA 18-50mm F4.5-5.6 DC WR RE's weight of 158g.
Filter Threads
The Pentax DA 18-50mm F4.5-5.6 DC WR RE has a filter size of 58mm 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 58mm filters that we recommend you to consider for the Pentax DA 18-50mm F4.5-5.6 DC WR RE:
And these are the 49mm filters that we recommend for the Pentax 40mm F2.8 L:
Lens Mounts
The Pentax DA 18-50mm F4.5-5.6 DC WR RE has the Pentax KAF3 lens mount whereas the Pentax 40mm F2.8 L has the Pentax KAF 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 KAF3 Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Pentax 40mm F2.8 L is also available in Pentax KAF mount.
Focal Range
Pentax DA 18-50mm F4.5-5.6 DC WR RE has a focal range of 18-50mm and
2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-75mm 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.
