Canon EF-S 18-200mm f/3.5-5.6 IS

Canon EF-S 18-200mm f/3.5-5.6 IS: Performance

High zoom ratio lenses like this Canon optic are often a compromise regarding optical quality. For a lens of this type, the performance holds up very well.

Shooting wide open at 18mm, sharpness in the centre of the image area already approaches very good levels, and clarity towards the edges of the frame is fairly good. Stopping down the aperture improves sharpness across the frame, peaking between f/5.6 and f/8, where sharpness in the centre is excellent and towards the edges it reaches very good levels.

At 80mm, the good sharpness in the centre is maintained at maximum aperture, with sharpness towards the edges dropping to fair levels. Peak quality across the frame is again achieved between f/8 and f/11 for this focal length, where sharpness across the frame is very good.

Finally at 200mm, good sharpness in the centre is still maintained at maximum aperture and fairly good sharpness levels towards the edges. Peak quality across the frame is attained at f/8 for this focal length and good sharpness across the frame is achieved.

Resolution at 18mm		Resolution at 80mm
Resolution at 200mm		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 7D using Imatest.

At shorter focal lengths Chromatic aberrations are kept below levels that may pose issues, even in large prints, or harsh crops from the edge of the frame. At 200mm chromatic fringing increases, exceeding two pixel widths towards the edges of the frame at f/5.6, which may start to become visible in images with high contrast edges near the edges of the frame.

Chromatic Aberrations at 18mm		Chromatic Aberrations at 80mm
Chromatic Aberrations at 200mm		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 7D using Imatest.

Falloff of illumination towards the corners of the frame is reasonably well controlled. At 18mm and f/3.5, the corners are 1.5 stops darker than the image centre and visually uniform illumination is achieved by f/5.6 at this focal length. At 200mm falloff increases as the corners are 1.7 stops darker than the centre and visually uniform illumination isn't achieved until the lens is stopped down to f/11 at this focal length.

Distortion is often an issue with high ratio zoom lenses like this. Imatest detected 6.13% barrel distortion at 18mm, which is quite a pronounced level and may pose issues in images with straight lines towards the edges of the frame. At 200mm 1.18% pincushion distortion is present, which is certainly less noticeable than the barrelling at 18mm. Luckily the distortion pattern is uniform across the frame, so correcting curved lines should be relatively straightforward in image editing software afterwards.

Canon don't supply lenses at this level with a lens hood, which is a shame as the optional EW-78D petal shaped hood would be a welcome addition. Even without a hood, this optic seems reasonably resistant to flare and loss of contrast caused by strong light sources just outside the frame although the lens does seem more susceptible to flare at 200mm than 18mm. Shooting into the light can cause a loss of contrast, especially at 200mm.

Wide angle - ISO100, 1/400, f/8, 18mm (35mm equiv – 28.8mm)		Telephoto - ISO100, 1/400, f/8, 200mm (35mm equiv – 320mm)
Contrast holds up reasonably well shooting into the light - ISO500, 1/60, f/5.6, 40mm (35mm equiv – 64mm)		The minimum focus distance of 45cm can be handy for close-up shooting - ISO320, 1/320, f/8, 200mm (35mm equiv – 320mm)
ISO100, 1/500, f/8, 70mm (35mm equiv – 112mm)		ISO100, 1/250, f/8, 90mm (35mm equiv – 144mm)
ISO100, 1/250, f/8, 28mm (35mm equiv – 44.8mm)		ISO100, 1/250, f/5, 60mm (35mm equiv – 96mm)

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