Canon's new EF-S 55-250mm f/4.0-5.6 IS is designed specifically for cameras with 'APS-C' sized sensors and combines light weight with a very low price tag for an optically-stabilised lens. On the EOS 400D and 40D cameras we used for our tests, its focal length range is equivalent to 88-400mm on a 35mm camera. It's a fairly slow lens - and this is apparent in the viewfinder when you're shooting.
Optical components consist of 12 elements arranged in 10 groups, with one ultra-low dispersion (UD) element in the front group to suppress secondary chromatic aberrations and minimise coloured fringing. The built-in optical image stabiliser claims to give up to four f-stops of shutter speed advantage. Super Spectra coatings control ghosting and flare by internal reflections.
Polycarbonate plastic has been used as the major construction material in the body of the lens to minimise weight cost-effectively. Canon claims only environmentally-friendly, lead-free glass is used in the construction of the lens - but makes no mention of possible plastic components (which can keep costs and weight down without compromising optical quality).
Build quality is good for a plastic lens and moving parts are acceptably tight. However, some care will be required when changing lenses as the lens mount is also made of plastic and, though appearing quite solid, may be vulnerable to chipping and (eventually) wear.
Both focusing and zoom rings have textured rubber coatings to provide a secure grip. The ridges on the focusing ring are narrower than those on the zoom ring and may trap grit. The zoom ring, which is 4cm long, lies nearest to the camera.
Behind the rubberised section on the zoom ring is a narrow aluminium band with engraved settings marking the 55mm, 70mm, 100mm, 135mm, 200mm and 250mm positions. Behind this ring, the lens carries slider switches for AF/MF and Stabiliser on/off settings. A white dot provides a position indicator for fitting the lens on a camera.
Aperture settings range from f/4.0 to f/22 at the 55mm setting and f/5.6 to f/32 at 250mm. At 250mm, the maximum magnification is 0.31x, which does not come into the true 1:1 macro range. The closest focusing distance is 1.1 metres.
Neither a distance scale nor indicators for depth of field or infrared adjustment are provided. The lens is supplied with end caps but no lens hood. A lens hood (ET-60) and lens case (LP1019) are available as optional accessories.
Margaret Brown
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