The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 16-45mm F4 ED AL and the Pentax DA 20-40mm F2.8-4 ED DC WR 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 16-45mm F4 ED AL is the longer of the two lenses at 92mm. The Pentax DA 20-40mm F2.8-4 ED DC WR with a length of 69mm, is 23mm shorter. Besides being longer, the Pentax 16-45mm F4 ED AL also has a larger diameter of 72mm compared to the Pentax DA 20-40mm F2.8-4 ED DC WR's 71mm 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 DA 20-40mm F2.8-4 ED DC WR weighs 283g, 20% (73g) lighter than the Pentax 16-45mm F4 ED AL's weight of 356g.
Filter Threads
The Pentax 16-45mm F4 ED AL has a filter size of 67mm whereas the Pentax DA 20-40mm F2.8-4 ED DC WR has a 55mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Pentax 16-45mm F4 ED AL:
And these are the 55mm filters that we recommend for the Pentax DA 20-40mm F2.8-4 ED DC WR:
Lens Mounts
The Pentax 16-45mm F4 ED AL has the Pentax 645AF2 lens mount whereas the Pentax DA 20-40mm F2.8-4 ED DC WR has the Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with these mounts are , and for the Pentax 645AF2 Mount and , and for the Pentax KAF3 Mount.
Focal Range
Pentax 16-45mm F4 ED AL has a focal range of 16-45mm and
2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
24-67.5mm when used on a APS-C / DX format camera.
On the other hand, the Pentax DA 20-40mm F2.8-4 ED DC WR has a focal range of 20-40mm and 2.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 30-60mm when used on a APS-C / DX format camera.
