The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 15-85mm f3.5-5.6 IS USM 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. Canon 15-85mm f3.5-5.6 IS USM is the longer of the two lenses at 88mm. The PENTAX28-105mm F3.5-5.6 WR with a length of 87mm, is 1mm shorter. Besides being longer, the Canon 15-85mm f3.5-5.6 IS USM also has a larger diameter of 82mm 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, 23% (135g) lighter than the Canon 15-85mm f3.5-5.6 IS USM's weight of 575g.
Filter Threads
The Canon 15-85mm f3.5-5.6 IS USM has a filter size of 72mm 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 72mm filters that we recommend you to consider for the Canon 15-85mm f3.5-5.6 IS USM:
And these are the 62mm filters that we recommend for the PENTAX28-105mm F3.5-5.6 WR:
Lens Mounts
The Canon 15-85mm f3.5-5.6 IS USM has the Canon EF-S lens mount whereas the PENTAX28-105mm F3.5-5.6 WR has the Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Focal Range
Canon 15-85mm f3.5-5.6 IS USM has a focal range of 15-85mm and
5.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
24-136mm 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.
