The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 24-105mm F3.5-5.6 IS STM and the Canon 18-135mm f3.5-5.6 IS 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 24-105mm F3.5-5.6 IS STM is the longer of the two lenses at 104mm. The Canon 18-135mm f3.5-5.6 IS with a length of 101mm, is 3mm shorter. Besides being longer, the Canon 24-105mm F3.5-5.6 IS STM also has a larger diameter of 83mm compared to the Canon 18-135mm f3.5-5.6 IS'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. Canon 18-135mm f3.5-5.6 IS weighs 455g, 13% (70g) lighter than the Canon 24-105mm F3.5-5.6 IS STM's weight of 525g.
Filter Threads
The Canon 24-105mm F3.5-5.6 IS STM has a filter size of 77mm whereas the Canon 18-135mm f3.5-5.6 IS 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 77mm filters that we recommend you to consider for the Canon 24-105mm F3.5-5.6 IS STM:
And these are the 67mm filters that we recommend for the Canon 18-135mm f3.5-5.6 IS:
Lens Mounts
The Canon 24-105mm F3.5-5.6 IS STM has the Canon EF lens mount whereas the Canon 18-135mm f3.5-5.6 IS has the Canon EF-S lens mount. Some of the latest released cameras that are compatible with these mounts are Canon 1D X III, Canon 6D MII and Canon 5D MIV for the Canon EF Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount.
Canon 18-135mm f3.5-5.6 IS is also available in Canon EF-S mount.
Focal Range
Canon 24-105mm F3.5-5.6 IS STM has a focal range of 24-105mm and
4.4X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
38.4 - 168mm.
On the other hand, the Canon 18-135mm f3.5-5.6 IS 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.