When it comes to DSLR image quality, pretty much all of us have heard the old truism about the quality of the lens being more important than the price of the camera. In this respect it pays to get off to the best possible start when buying your first DSLR, or when taking your first steps towards building a lens collection.
Thing is, good lenses like Sigma 17-50mm f/2.8 EX DC OS HSM cost money, and when purchasing a DSLR most people are much more likely to spend as much as they can on the camera and settle for a cheap kit lens, more often than not with a focal range of between 18-55mm; a so-called 'standard zoom'. This is wide enough to shoot landscapes and groups of people, while also having enough reach to cater for individual portraits and to isolate nearby subjects from their surroundings.
While there’s no denying the flexibility a standard zoom offers, many kit lenses tend to be a bit flimsy and plasticky. In addition they usually offer a maximum aperture that starts at f/3.5 at 18mm, progressively stopping down to f/5.6 by the time you reach 50mm or 55mm.
The Sigma 17-50mm f/2.8 EX DC OS HSM lens (herein referred to as the ‘Sigma 17-50mm’), by contrast, takes things up several notches in all areas, from general build quality to performance. Specifically designed for use with DSLRs fitted with an APS-C sensor, it’s a much larger and more solid optic than your standard kit zoom.
Just as importantly (if not more so) it also offers a fast f/2.8 aperture throughout its focal range. Not only will this allow you to shoot at higher shutter speeds in poor light, it can also be used creatively to create a shallow depth of field that keeps your main subject sharp while throwing the background out of focus. Judged purely on its merits as a creative tool, a standard zoom with a constant f/2.8 like this is extremely useful.
In this respect the Sigma 17-50mm we have on test here represents a significant upgrade over your standard kit lens. But at around £550 it’s not cheap. Sure, you can probably recoup around £100 if you were to buy your DSLR as a body-only option rather than going for the kit lens package. But is the Sigma 17-50mm worth this extra investment? And does it merit a closer look at full price if you already own a kit lens of a similar focal range? Let’s take a closer look at what it delivers for the extra outlay.