Canon EF-S 18-135mm f/3.5-5.6 IS STM Lens Review

Canon EF-S 18-135mm f/3.5-5.6 IS STM Performance

At maximum aperture and 18mm sharpness is already exceelnt in the centre of the frame, with the clarity towards the edges of the frame being not too far behind. Peak sharpness is achieved between f/4 and f/5.6 for this focal length, and sharpness is excellent across the frame at these apertures.

With the lens zoomed to 50mm, sharpness at maximum aperture remains very high, with excellent clarity being recorded across the frame by Imatest. Peak sharpness across the frame is achieved between f/5.6 and f/8 for this focal length where sharpness is excellent across the frame.

As is usually the case with zoom lenses covering a wide range of focal lengths, sharpness falls away somewhat at maximum telephoto. Still, at f/5.6 clarity in the centre of the frame is still very good, although the quality achieved towards the edges of the frame drops to fairly good levels. Peak sharpness across the frame is achieved between f/8 and f/11 at 135mm.

Resolution at 18mm		Resolution at 50mm
Resolution at 135mm		How to read our charts The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple. For this review, the lens was tested on a Canon EOS 650D using Imatest.

Chromatic aberrations are reasonably prevalent throughout the zoom range, regularly exceeding one pixel width. These high levels of CA may pose issues, especially in images with high contrast edges.

Chromatic aberration at 18mm		Chromatic aberration at 50mm
Chromatic aberration at 135mm		How to read our charts Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements aspheric, extra-low dispersion etc. to minimize the problem, hence they usually cost more. For this review, the lens was tested on a Canon EOS 650D using Imatest.

Falloff of illumination towards the corners of the frame is reasonably well controlled. At 18mm the corners are 1.38 stops darker than the image centre at maximum aperture and visually uniform illumination is achieved with the aperture stopped down to f/5.6 and beyond. At 135mm the corners are 1.01 stops darker than the image centre and visually uniform illumination is achieved at f/8 and beyond.

Distortion is pretty well controlled for a super-zoom lens, with Imatest detecting 3.8% barrel at 18mm at 0.869% pincushion at 135mm. This level of distortion should pose few issues for general snaps, but may be too much for discerning photographers. If straight lines are paramount, then you'll be glad to hear that the distortion pattern is uniform across the frame, which should make corrections relatively straightforward to apply.

No issues with flare were encountered during testing, with only a slight loss of contrast being noticeable when shooting directly into the light at wide apertures. However, no lens hood is supplied as standard, so if you require one for peace of mind, then an EW-73B hood can set you back up to £30.

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