Camera Accessories

Released concurrently with the EOS 5D, Canon's EF 70-300mm f/4-5.6 IS USM telephoto zoom lens replaces the 10-year-old EF 75-300mm f/4-5.6 IS USM lens. We tested it on Canon's new EOS 30D, where it covered a focal length range equivalent to 112-480mm in 35mm film format. The new lens combines ultra-low dispersion (UD) and aspherical lens elements and includes an improved optical image stabiliser (IS) that allows users to shoot at approximately three shutter speeds slower than a non-stabilised lens. This is a one-stop improvement over its predecessor.

The IS system is based on gyro sensors, which compensate for vibrations by shifting a correcting lens group perpendicular to the optical axis. This alters the light path, returning the image to its correct position on the sensor or film plane. Two stabilisation modes are provided: Mode 1 steadies the image along both the horizontal and vertical axes, while Mode 2, which is used for panning to follow a moving subject, turns off correction in the panned direction and prevents the effect of dragging the subject back through the frame. IS switches off automatically when the camera is mounted on a tripod to prevent feedback loops between the IS sensor and stabiliser motor vibrations. It can also be switched off manually.

The EF 70-300mm f/4-5.6 IS USM lens is clearly aimed at enthusiast photographers, especially those who don't want to include a heavy tripod in their packs. Less than half the price of Canon's 'DO' (diffractive optics) model with the same zoom range, it is also longer and slimmer - as well as almost 100 grams lighter. However, it remains a relatively long lens by today's standards, measuring 142.8mm at the 70mm setting and 197.8mm when fully extended.

The wide zoom ring, which is roughly midway along the lens barrel, rotates very easily - almost too easily at times - and is slightly loose when extended. Fortunately it can be locked at the 70mm position to prevent it from sliding out when the camera and lens are being carried. The manual focus ring is also slightly slack.

A switch near the base of the lens lets users select between auto and manual focusing. The latter is adjusted via a narrow ring near the front of the lens barrel. The iris diaphragm has eight blades and provides a circular aperture, with minimum apertures of f32-38, depending on the focal length setting.

The new 70-300mm lens is compatible with the E-TTL II flash system in the latest EOS digital cameras.  When used with Canon's EX Speedlite flash units, it passes distance information to the flash algorithm, delivering more accurate flash exposure metering.

Handling and Performance

Despite its length, the EF 70-300mm lens felt equally comfortable and well-balanced on both the EOS 30D and lighter EOS 300D cameras. For shots taken in bright light, with the sun above or to the rear, it produced images with good sharpness and colour saturation, even at full aperture. In back-lit situations, contrast was slightly reduced but sharpness remained generally good, although not superb. Even though the lens was supplied without a lens hood, we found no evidence of flare or ghosting with moderately backlit subjects and colour fringing was not evident. This means the Super Spectra lens coatings and lens element shaping are effective.

Imatest showed overall resolution to be slightly lower than that of the 18-55mm lens supplied with the EOS 30D. Images were also slightly softened at the corners at the 70mm setting with the widest aperture although this softening had vanished by 135mm and was eliminated by stopping down beyond f8. Slight pincushioning was detected at 200mm and beyond, and saturation was slightly lower than the 18-55mm lens. No chromatic aberration was detected and none of the defects we found proved problematic for general shooting.

The IS system worked extremely well, and Canon's claims of a three stop exposure advantage proved credible. For most brightly-lit subjects, autofocusing was fast and accurate, thanks to the ultrasonic motor, which operated almost silently. However, in very dim lighting and at focal lengths beyond 200mm with detailed, backlit subjects like grasses or leaves, the lens had a strong tendency to 'hunt' and manual focusing was necessary. The 8-bladed iris produced attractive out-of-focus backgrounds at wide apertures. (28)

Focal length range: 70-300mm
Maximum aperture: f4.5-5.6
Lens construction: 15 elements in 10 groups
Minimum focus: 1.5 m at all focal lengths
Filter size: 58mm
Lens mount: Canon EF
Dimensions (diameter x L): 76.9mm x 142.8mm
Weight: 630g