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 Canon 15-85mm f3.5-5.6 IS USM 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 Canon 15-85mm f3.5-5.6 IS USM with a length of 88mm, is 6mm shorter. On the other hand, the Canon 15-85mm f3.5-5.6 IS USM has a larger diameter of 82mm compared to the Pentax 17-70mm F4.0 AL SDM's 75mm 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 17-70mm F4.0 AL SDM weighs 485g, which means it is 90g (15%) lighter than the Canon 15-85mm f3.5-5.6 IS USM which has a weight of 575g.
Filter Threads
The Pentax 17-70mm F4.0 AL SDM has a filter size of 67mm whereas the Canon 15-85mm f3.5-5.6 IS USM has a 72mm 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 72mm filters that we recommend for the Canon 15-85mm f3.5-5.6 IS USM:
Lens Mounts
The Pentax 17-70mm F4.0 AL SDM has the Pentax KAF3 lens mount whereas the Canon 15-85mm f3.5-5.6 IS USM has the Canon EF-S lens mount. Some of the latest released cameras that are compatible with these mounts are , and for the Pentax KAF3 Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount.
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 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.
