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 and the Tokina 16.5-135mm f3.5-5.6 DX for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Canon 18-135mm F3.5-5.6 IS is the longer of the two lenses at 96mm. The Tokina 16.5-135mm f3.5-5.6 DX with a length of 78mm is 18mm shorter. On the other hand, the Tokina 16.5-135mm f3.5-5.6 DX has a larger diameter of 84mm compared to Canon 18-135mm F3.5-5.6 IS's 77mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Canon 18-135mm F3.5-5.6 IS weighs 515g, which means it is 95g (15%) lighter than the Tokina 16.5-135mm f3.5-5.6 DX which has a weight of 610g.
Lens Mounts
Both Canon 18-135mm F3.5-5.6 IS has the Canon EF-S lens mount whereas the Tokina 16.5-135mm f3.5-5.6 DX 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 T8i, Canon 90D and Canon SL3 for the Canon EF Mount.
Canon 18-135mm F3.5-5.6 IS is also available in Canon EF-S mount.
Tokina 16.5-135mm f3.5-5.6 DX is also available in Nikon F (DX) mount.
Focal Range
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. Tokina 16.5-135mm f3.5-5.6 DX has a focal range of 17-135mm and 7.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-216mm when used on a APS-C / DX format camera.