The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 16-85mm F3.5-5.6 ED DC WR and the Olympus ED 12-40mm f2.8 PRO 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 16-85mm F3.5-5.6 ED DC WR is the longer of the two lenses at 94mm. The Olympus ED 12-40mm f2.8 PRO with a length of 84mm, is 10mm shorter. Besides being longer, the Pentax 16-85mm F3.5-5.6 ED DC WR also has a larger diameter of 78mm compared to the Olympus ED 12-40mm f2.8 PRO's 70mm diameter.
ss
Below you can find a scaled side-by-side image of Pentax 16-85mm F3.5-5.6 ED DC WR and Olympus ED 12-40mm f2.8 PRO to get a better idea of how their sizes compare in real life.
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. Olympus ED 12-40mm f2.8 PRO weighs 382g, 21% (106g) lighter than the Pentax 16-85mm F3.5-5.6 ED DC WR's weight of 488g.
Filter Threads
The Pentax 16-85mm F3.5-5.6 ED DC WR has a filter size of 72mm whereas the Olympus ED 12-40mm f2.8 PRO has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Pentax 16-85mm F3.5-5.6 ED DC WR:
And these are the 62mm filters that we recommend for the Olympus ED 12-40mm f2.8 PRO:
Lens Mounts
The Pentax 16-85mm F3.5-5.6 ED DC WR has the Pentax KAF3 lens mount whereas the Olympus ED 12-40mm f2.8 PRO has the Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and OM System OM-1 II, Panasonic G9 II and OM System OM-5 for the Micro Four Thirds Mount.
Focal Range
Pentax 16-85mm F3.5-5.6 ED DC WR has a focal range of 16-85mm and
5.3X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
24-127.5mm when used on a APS-C / DX format camera.
On the other hand, the Olympus ED 12-40mm f2.8 PRO has a focal range of 12-40mm and 3.3X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 24-80mm when used on a FourThirds format camera.