The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 18-135mm f3.5-5.6 IS STM and the Canon 28-105mm f4.0-5.6 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. Canon 18-135mm f3.5-5.6 IS STM is the longer of the two lenses at 96mm. The Canon 28-105mm f4.0-5.6 USM with a length of 68mm, is 28mm shorter. Besides being longer, the Canon 18-135mm f3.5-5.6 IS STM also has a larger diameter of 77mm compared to the Canon 28-105mm f4.0-5.6 USM's 67mm 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. Canon 28-105mm f4.0-5.6 USM weighs 210g, 56% (270g) lighter than the Canon 18-135mm f3.5-5.6 IS STM's weight of 480g.
Filter Threads
The Canon 18-135mm f3.5-5.6 IS STM has a filter size of 67mm whereas the Canon 28-105mm f4.0-5.6 USM has a 58mm 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 Canon 18-135mm f3.5-5.6 IS STM:
And these are the 58mm filters that we recommend for the Canon 28-105mm f4.0-5.6 USM:
Lens Mounts
The Canon 18-135mm f3.5-5.6 IS STM has the Canon EF-S lens mount whereas the Canon 28-105mm f4.0-5.6 USM has the Canon EF 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 Canon 1D X III, Canon 6D MII and Canon 5D MIV for the Canon EF Mount.
Focal Range
Canon 18-135mm f3.5-5.6 IS STM has a focal range of 18-135mm and
7.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-216mm when used on a APS-C / DX format camera.
On the other hand, the Canon 28-105mm f4.0-5.6 USM has a focal range of 28-105mm and 3.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 44.8 - 168mm.