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 Pentax 17-70mm F4.0 AL SDM 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. Pentax 17-70mm F4.0 AL SDM weighs 485g, 0% (3g) lighter than the Pentax 16-85mm F3.5-5.6 ED DC WR's weight of 488g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Pentax KAF3 Mount for size comparison purposes.
Standard Lenses in Pentax KAF3 Mount for Size Comparison
Filter Threads
The Pentax 16-85mm F3.5-5.6 ED DC WR has a filter size of 72mm whereas the Pentax 17-70mm F4.0 AL SDM 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 72mm filters that we recommend you to consider for the Pentax 16-85mm F3.5-5.6 ED DC WR:
And these are the 67mm filters that we recommend for the Pentax 17-70mm F4.0 AL SDM:
Lens Mounts
Both the Pentax 16-85mm F3.5-5.6 ED DC WR and the Pentax 17-70mm F4.0 AL SDM has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
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 Pentax 17-70mm F4.0 AL SDM has a focal range of 17-70mm and 4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 25.5-105mm when used on a APS-C / DX format camera.
