The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 17-70mm F4.0 AL SDM and the PENTAX28-105mm F3.5-5.6 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 17-70mm F4.0 AL SDM is the longer of the two lenses at 94mm. The PENTAX28-105mm F3.5-5.6 WR with a length of 87mm, is 7mm shorter. Besides being longer, the Pentax 17-70mm F4.0 AL SDM also has a larger diameter of 75mm compared to the PENTAX28-105mm F3.5-5.6 WR's 73mm 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. PENTAX28-105mm F3.5-5.6 WR weighs 440g, 9% (45g) lighter than the Pentax 17-70mm F4.0 AL SDM's weight of 485g.
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 17-70mm F4.0 AL SDM has a filter size of 67mm whereas the PENTAX28-105mm F3.5-5.6 WR 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 67mm filters that we recommend you to consider for the Pentax 17-70mm F4.0 AL SDM:
And these are the 62mm filters that we recommend for the PENTAX28-105mm F3.5-5.6 WR:
Lens Mounts
Both the Pentax 17-70mm F4.0 AL SDM and the PENTAX28-105mm F3.5-5.6 WR has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are , and .
Focal Range
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.
On the other hand, the PENTAX28-105mm F3.5-5.6 WR has a focal range of 28-105mm and 3.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42 - 157.5mm.
