Shading
Shading is visible wide open at 10mm, illustrated by the graphic. This kind of sudden fall-off in the corners can be obvious in some pictures, but is easy enough to fix in post-processing if desired. It also reduces on stopping down or zooming in, so isn’t a problem most of the time.
image:http://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/13/2014/08/Canon_EF_S_10_18mm_f4.5_5.6_IS_STM_shading.jpg
Curvilinear distortion
Typically for this kind of lens, the 10-18mm zoom shows visible barrel distortion at wideangle, although it’s not at all excessive. The relatively simple profile also makes it easy to fix. It reduces progressively on zooming in, and at 18mm there’s barely any distortion at all.
image:http://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/13/2014/08/Canon_EF_S_10_18mm_f4.5_5.6_IS_STM_curvilinear_distortion.jpg
Our verdict
Despite its ultra-wideangle, I’d happily use the Canon 10-18mm f/4.5-5.6 as a walk-around lens with a mid-range prime such as the EF 50mm f/1.4 in my camera bag. At its widest aperture the depth of field avoids being shallow, keeping large groups in focus, but with this being an ultra-wide lens it’s important to remember that people and features near the edges of the frame will be stretched slightly.
Taking its price and performance into account, this has got to be a must-have lens for any Canon APS-C camera owner who is interested in shooting landscape and cityscape images. At such a competitive price, it’s hard to think of a reason not to include this in your lens collection if you’re looking to expand.