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 Sigma 18-250mm F3.5-6.3 DC OS HSM 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. Sigma 18-250mm F3.5-6.3 DC OS HSM is the longer of the two lenses at 101mm. The Canon 18-135mm F3.5-5.6 IS with a length of 96mm, is 5mm shorter. Besides being longer, the Sigma 18-250mm F3.5-6.3 DC OS HSM also has a larger diameter of 79mm compared to the Canon 18-135mm F3.5-5.6 IS's 77mm 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 515g, which means it is 113g (17%) lighter than the Sigma 18-250mm F3.5-6.3 DC OS HSM which has a weight of 628g.
Filter Threads
The Canon 18-135mm F3.5-5.6 IS has a filter size of 67mm whereas the Sigma 18-250mm F3.5-6.3 DC OS HSM 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 Canon 18-135mm F3.5-5.6 IS:
And these are the 72mm filters that we recommend for the Sigma 18-250mm F3.5-6.3 DC OS HSM:
Lens Mounts
The Canon 18-135mm F3.5-5.6 IS has the Canon EF-S lens mount whereas the Sigma 18-250mm F3.5-6.3 DC OS HSM 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 the Canon EF-S mount.
Sigma 18-250mm F3.5-6.3 DC OS HSM is also available in Canon EF , Nikon F (DX), Pentax KAF3, Sony Alpha, Sigma SA, Nikon F (DX), Pentax KAF3, Sony Alpha and Sigma SA mounts.
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.
On the other hand, the Sigma 18-250mm F3.5-6.3 DC OS HSM has a focal range of 18-250mm and 13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-400mm when used on a APS-C / DX format camera.
