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 Panasonic 8-18mm F2.8-4.0 ASPH 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. Panasonic 8-18mm F2.8-4.0 ASPH weighs 315g, 45% (260g) 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 Panasonic 8-18mm F2.8-4.0 ASPH 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 Canon 15-85mm f3.5-5.6 IS USM:
And these are the 67mm filters that we recommend for the Panasonic 8-18mm F2.8-4.0 ASPH:
Lens Mounts
The Canon 15-85mm f3.5-5.6 IS USM has the Canon EF-S lens mount whereas the Panasonic 8-18mm F2.8-4.0 ASPH has the Micro Four Thirds 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 OM System OM-3 Astro, OM System OM-5 II and OM System OM-3 for the Micro Four Thirds 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 Panasonic 8-18mm F2.8-4.0 ASPH has a focal range of 8-18mm and 2.3X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 16-36mm when used on a FourThirds format camera.
