The kit lenses you get with digital SLRs aren’t generally that good. They might be sharp enough, but their specifications and handling leave something to be desired. The Tamron 17-50mm f2.8 could be the answer, offering a significant step up in features, versatility and, perhaps, performance.

It’s a direct replacement for the 18-55mm kit lenses you typically get with an SLR, but this one has two big bonuses: a constant maximum aperture and Tamron’s VC (Vibration Control) anti-shake system.

It’s one of Tamron’s ‘Di II’ lenses, which are designed specifically for the APS-C sized sensors of digital SLRs. It can’t be used on a full-frame D-SLR or 35mm film camera. For this you need to be looking at Tamron’s ‘Di’ (‘digitally integrated’) range instead.

The f2.8 constant maximum aperture will be a big selling point for keen photographers. It makes this lens around half a stop faster than the average kit zoom at its minimum focal length and a massive two stops faster at full zoom. The wider apertures mean you can shoot in lower light levels without risking camera shake, and you don’t have to keep adapting to different maximum apertures at different zoom settings. This is especially useful if you like to shoot in manual exposure mode, where you’ll often find yourself taking a light reading and then weighing up different shutter speed/aperture combinations.

Tamron’s Vibration Control system adds to this lens’s low-light capabilities. It detects any camera movement during the exposure and counteracts it by instantly moving a floating element within the lens to compensate. It works in three axes to counter all kinds of shake and movement, and in the test shots taken for this review it gave sharp images at shutter speeds 2-3 stops slower than normal. The VC system kicks in when you half-press the shutter release, and you can hear the motors whirring quietly in the background as you frame the picture.

Despite the inclusion of the Vibration Control mechanism, this lens is only a little longer and heavier than its non-stabilised predecessor. That’s no mean achievement, given the size of the internal elements needed in an f2.8 constant aperture zoom.

There are 19 of these elements, arranged in 14 groups, which is a fairly complex design that inevitably makes this lens heavier than your average kit zoom. Compared to the constant-aperture 17-55mm zooms from Canon and Nikon, though, the Tamron is pretty compact. (It’s also around half the price.)

The zoom action is moderately heavy but there are no sticking points anywhere and only a single barrel extension, which feels pretty firm. There is a zoom lock on the lens barrel, but you’d probably end up using this just for storage and transit, since there’s no tendency towards zoom creep in everyday use. The internal focusing system means that the front element doesn’t rotate, so it’s fine for filters.

Focusing could be the weak point, if there is one. There’s no full-time manual override, so you’ll need to use the AF/MF switch on the side to override the camera. There is a distance scale on the manual focus ring, which has a very smooth and light action, though the focus travel is quite short.

Tamron has incorporated autofocus motors into this lens, which means that you don’t have to rely on the motor in the camera body. Just as well if you own one of Nikon’s cheaper, smaller camera bodies because these dispense with the AF motor altogether. The autofocus is pretty snappy, though it’s not quite as fast or as quiet as Canon’s USM or Nikon’s SWM lenses. These things are relative, of course, and to put it in perspective most Pentax and Sony lenses are a good deal noisier.

Overall, the Tamron’s finish and handling are very good. It’s a lot cheaper than comparable lenses from Canon and Nikon, but it doesn’t feel it. But will the price difference become apparent in the picture quality?

Not really. The Tamron does suffer from fairly heavy barrel distortion at the wideangle end of the zoom range, and it has to be stopped down to f4 or f5.6 to deliver its true sharpness, but this is pretty normal with constant-aperture zooms and the results from our tests were really very good. Interestingly, the test charts show it to be sharpest in the middle of the zoom range, and it also holds up well at maximum focal length, which is where most zooms tend to deteriorate.

If you have invested heavily in good Canon or Nikon systems it’s easy to see why you might prefer to stick with your camera maker’s own lenses, but for those on a tight budget the Tamron 17-50mm is an excellent alternative, providing similar levels of performance at a much lower price.

Final Verdict It’s not all about zoom range. A constant-aperture zoom like this one will open up your photography in other ways, and the Tamron gives you a lot for your money. OVERALL

Our lens reviewer, and technical expert, Rod is a veritable photographic encyclopaedia. His illustrious CV has seen him write for many mags, websites and journals.