The image-stabilised 18-55mm gives a good account of itself in our tests, and is clearly much improved over the old kit lens which we've grown to know and not quite love over the last few years. It distinctly outperforms the more expensive 17-85mm at wide angle, and matches it over most of the rest of its range; however this is tempered by a slightly disappointing performance at telephoto.
|Sharpness||A very impressive performance for a kit lens, giving good resolution across the field from 18mm though to 35mm even wide open, and with little sharpness benefit from stopping down. However at 55mm the story changes, and the lens is disappointingly soft in the corners wide open, only really reaching acceptable levels at F8-F11. As usual, stopping down beyond F11 causes the image to degrade due to diffraction, and anything below F16 starts to look pretty unusable.|
|Chromatic Aberration||This lens clearly shows Canon starting to confront their CA demons. The unusual shape of the curves suggests an active attempt to re-correct chromatic aberration towards the corners, where it is normally most visible. This apparently comes at the price of unusual behaviour in the blue channel at the centre of the frame, most visible wide open; this displays as CA in our graphs, but is in fact an overall blue 'colour blur' effect, and disappears completely on closing the aperture down one stop.|
|Falloff||We consider falloff to start becoming perceptible when the corner illumination falls more than 1 stop below the centre. There’s little to worry about with this lens, presumably (at least in part) a result of the enlarged front elements compared to the old 18-55mm; fall-off will only be visible wide open at 18mm, and disappears when stopping down even slightly.|
|Distortion||As usual distortion is most pronounced at wideangle, with 1.4% barrel at 18mm. This is a complex distortion, with the effect most pronounced towards the centre, then pinched in again towards the edges, so relatively difficult to correct in software. At 28mm the lens is almost perfectly corrected, and at longer focal lengths the pattern changes to pincushion, at its worst reaching a just-perceptible -0.6% at 50mm.|
Specific image quality issues
Like most kit zooms, the 18-55 IS is rather prone to flare in bright light, something which is not really helped by the pretty ineffective hood. The samples below exhibit fairly severe flare effects, most visible on the right side of the frame, in both cases due to strong off-axis light sources. The problem lies at least in part with the cheap construction of the lens, which simply makes it less effective at suppressing internal reflection of stray light. This also results in lower overall image contrast when compared to more expensive lenses such as the 17-85mm IS USM.
|18mm F16||30mm F8.0|
Optical Image Stabilisation
Canon claim that the new image stabilisation unit developed for this lens (along with its sister 55-250mm telezoom) is at least as effective as the more complex unit on higher end lenses such as the 17-85mm IS USM, allowing hand-holding at shutter speeds four stops slower than usual without seeing blur from camera shake. The stabiliser is almost completely silent and free of vibration in operation, and aside from the stabilising effect on the viewfinder image, you’ll hardly notice it operating at all.
We tested the IS system at both the long and short ends of the zoom range in our standard studio test. With its effective focal length range of 29-88mm, we'd normally expect to be able to get good results handheld at 1/30 sec at wideangle, and 1/90 sec at telephoto without image stabilisation. The subject distance for these tests was approximately 2.5m.
|18mm IS OFF||55mm IS OFF|
|18mm IS ON||55mm IS ON|
The results here a generally similar to those we obtained with the 17-85mm IS, confirming the effectiveness of Canon's new simplified image stabilization unit. At 18mm and a shutter speed of 1/6 sec, IS is delivering 50% critically sharp shots, compared to just 10% without. Even at the very slow shutter speed of 0.3 sec, IS is giving usable images with no more than mild blur 70% of the time; we obtained none whatsoever with it switched off.
Performance is just as good at the telephoto end; at 1/25 sec, IS gives 80% sharp images in contrast to 20% sharp without IS; and at 1/6 sec, 80% of images are usable with IS turned on, in comparison to none at all with it turned off. Overall the optical image stabilization genuinely does confer a very useful advantage when handholding the camera.