Camera Accessories

Designed to provide a wide zoom range in a compact and lightweight form factor, Canon's EF-S18-200mm f/3.5-5.6 IS telephoto zoom lens can only be used with cameras that have 'APS-C-sized' image sensors. Supporting a zoom range of approximately 11 times, it covers a focal length equivalent to 29-320mm in 35mm format but weighs only 595 grams. Built-in image stabilisation provides approximately four f-stops of shutter speed advantage and the stabilisation system can detect when the camera is panned.

Consisting of 16 elements in 12 groups, this lens is made from environmentally friendly lead-free glass and contains UD glass and high-precision aspheric elements. Internal Focus (IF) mechanisms provide smooth focusing and make it easy to use angle-critical filters, such as polarisers and graduates. The lens comes with front and end caps but no lens hood; although an EW-78D lens hood is available as an optional accessory. 

A gear-driven micro-motor system is used for autofocusing, instead of the USM ring-type motors found in many other Canon lenses, which are faster and more accurate. The lens also carries electronic contacts that provide information for E-TTL II flash metering.

A small zoom lock button is located near the camera end of the lens barrel on the lower right corner, where it is (just) reachable when the camera is in use. It's necessary as the lens tends to extend when it is carried facing downwards on the camera.

Mounted on the side of the lens barrel are two slider switches. The top switch covers auto and manual focus while the lower switch is for turning the image stabiliser on and off.  

Handling
Like most consumer-level lenses, the EF-S18-200mm f/3.5-5.6 IS lens is made mainly from polycarbonate, although it sports a stainless steel mounting plate, which sets it marginally above entry-level lenses. The filter ring, however, is plastic and accepts a 72mm filter. The review lens was a comfortable match for the EOS 50D body we used for our tests and its build quality was in line with Canon's mid-level consumer lenses.

Both the zoom ring and focusing ring have ridged rubber coatings which provide a good grip. The focusing ring, which is located near the front of the lens is significantly narrower than the zoom ring. It rotates when the camera is in AF mode and manual focusing is only possible when the switch is set to the MF position. In manual mode it rotates through just over a quarter of a turn. The ring itself moves a little too easily for our taste but provides adequate precision for most applications.

The zoom ring is 33mm wide and has wider ridging than the focusing ring. It rotates through almost half a turn as you move from the 18mm to the 200mm position and extends the front of the lens by six centimetres. Maximum and minimum apertures also change as you adjust the lens focal length, as shown in the table below.

Performance
The focusing motor on the test lens was fairly noisy and not particularly fast.  Focusing accuracy was patchy in low light and low-contrast conditions and the ability of the lens to track fast-moving subjects was somewhat limited. However the image stabilisation system delivered the claimed four-stop shutter speed advantage, even at the 200mm setting, where we were able to use shutter speeds as slow as 1/8 second with the camera hand-held.

Photo Review wasn't able to run Imatest tests across the entire focal length range because we don't have enough distance leeway in our testing set-up. However, we can present results for all focal lengths except the 200mm setting. 

Imatest showed the review lens was prone to edge softening at wide lens apertures. This was confirmed by subjective assessment of test shots, although in many cases you had to look closely to detect it. Centre resolution was highest at apertures between f/5 and f/14, but declined sharply from f/14 onwards and was very low near the minimum aperture settings (which we would consider unusable). The graph below shows the results of our tests.

Lateral chromatic aberration fell mostly in the 'low' band, as shown in the graph below. Note: the red line marks the boundary between negligible and low CA values, while the green line shows the point where 'low' changes to 'moderate'.

Barrel distortion was noticeable at the 18mm focal length. However, by 24mm images were close to distortion-free. We found slight pincushioning at the 50mm focal length, which continued to 135mm but was never enough to cause problems in normal use. No vignetting was observed, even when the lens aperture was wide open.

Backlit shots showed neither flare nor ghosting and contrast remained relatively high when the sun was just outside the imaging field. Bokeh was generally pleasing. 

SAMPLE IMAGES

18mm focal length, ISO 100, 1/125 second at f/16.

200mm focal length, ISO 100, 1/125 second at f/16.

 
200mm focal length, 1/8 second at f/8 - image stabilisation set to Off.

200mm focal length, 1/8 second at f/8 - image stabilisation set to On.

 
Backlighting  200mm focal length, 1/125 second at f/9.

130mm focal length, 1/200 second at f/6.4.

 
135mm focal length, 1/500 second at f/9.

70mm focal length, 1/60 second at f/5.0.

200mm focal length, 1/200 second at f/5.6.

155mm focal length, 1/320 second at f/6.3.

110mm focal length, 1/160 second at f/5.6.

200mm focal length, 1/80 second at f/8.

Picture angle: 74 degrees to 8 degrees
Maximum aperture: f/3.5-5.6
Minimum aperture: f/22-36
Lens construction: 16 elements in 12 groups (includes UD and aspherical elements)
Lens mount: Canon EF-S
Diaphragm Blades: 6 rounded
Minimum focus: 45 cm
Optical stabilisation: Yes
Filter size:  72 mm
Dimensions (Diameter x L): 78.6 x 102 mm
Weight: 595 grams