The words “Fast F2.8 Standard Zoom” describing a lens may not have the same instant mystique and cachet as say, “ultrawide” and “supertelephoto.” But for many a breed of photographer–wedding and location portrait specialists, for example–there’s no mistaking the importance of this workhorse lens. For APS-C shooters, the Sigma 17-50mm F2.8 EX DC OS HSM is a gigantic leap upwards in terms of overall performance compared to the variable aperture standard zoom kit lenses shipped with so many DSLRs.
Kit lenses are a great way to get started and learn, but when it comes to professional-quality results to satisfy the most discriminating photographers–not to mention their paying clients–the fast, constant-aperture standard zoom is the way to go. At first, it might seem redundant to purchase glass like the Sigma 17-50mm F2.8 EX DC OS HSM when there’s likely already a variable aperture kit lens in the bag that covers virtually the same focal range. And yes, the desire to add a longer, or wider, specialty lens is a strong urge, and maybe you’ll add one of those to your kit first. But whenever you do decide to swap the kit lens for a fast F2.8 standard zoom, you’ll immediately notice the advantages. You might say the difference between a variable aperture kit and a fast constant-aperture standard zoom is night and day; but I’ll choose to say it in terms of F/stops and bokeh.
The Sigma 17-50mm F2.8 EX DC OS HSM (fullframe equivalency: approximately 28-80mm on 1.6x APS-C cameras) zooms a bit wider, and a bit longer, than normal perspective while keeping the maximum aperture at a fast F2.8 all the while. And it captures this focal range for exceptional, professional-quality results. In fact, the testing lab, DXOMark.com states that its “tests tend to prove that the Sigma 17-50mm F2.8 EX DC OS HSM Nikon is so good that it even surpasses its competitors from Nikon and Canon which are twice as expensive.”
This is a few stops slower than a fixed F1.4 standard prime, but what you gain in terms of compositional versatility without having to physically relocate to reframe is very well worth it when you are not in total control of the situation. In other words, with a quick rack of the zoom, you can quickly and easily frame much tighter or looser as a wedding ceremony unfolds without having to swap lenses, or shooting position. And this very well may make the difference between missing a key moment as you juggle gear, or causing a bit of ruckus as you race through the chapel to recompose!
Variable aperture zooms always lose light-gathering ability as you zoom to longer focal lengths–that’s just how it works with optical physics. And the difference between F5.6 and F2.8 at maximum zoom is the difference between ISO 1600 and ISO 400, or between 1/15 second and 1/60 second. And that may very well be the difference between sharp, low-noise images, and motion-blurred shots with ugly shadow artifacts in the captured memories of a client. (Remember, Optical Stabilizer can only minimize camera motions during capture, as explained in great depth here.)
Another key benefit of a constant-aperture zoom is that there’s no shift of exposure or overriding of settings as you zoom, which happens with variable aperture lenses. So, if you are in metered manual mode, and you’ve locked in an exposure off a bride’s blushing cheek, you can easily zoom in or out without seriously impacting your creative decisions. If you’ve decided on 1/100 @ F2.8 at 17mm and then want to quickly zoom in for a magic expression, you’ll still get 1/100 @ F2.8 at 50mm. Try the same thing with an 18-55mm F3.5-5.6 kit lens @ 1/80 at 18mm and zoom in to 55mm @ F5.6 and your shutter speed is going to have to drop a few stops, or the ISO will have to climb. Or depending on your particular camera settings, you may wind up underexposing the shot by a few stops if you zoom in and it keeps with your manual decisions. There’s a workaround, which is to limit your maximum aperture to the variable aperture maximum, but this isn’t necessarily a great way to go.
And of course, the same holds true with lighting. If you’ve got a couple of non-TTL studio heads on light stands, you’re going to want to lock in your exposure settings on your camera. And if you’ve got a kit variable aperture standard zoom on your camera, that limits you to making sure you’re stopped down to the maximum value at telephoto to make sure you don’t seriously blow out the exposures as you go wider. (In other words, when shooting with studio strobes with a variable aperture zoom, you’ve got to make the lens act as though it is only capable of it maximum telephoto aperture at all focal lengths…to make it act like a much slower constant-aperture zoom!)
The focal range of the standard zoom lens is great for capturing people in the environment. You can go wider to make it more of an overall scene-setting shot, and then zoom in to tighten the composition and soften the bokeh even more while still painting the environment’s signature elements in the background–soft, with lovely separation, but still recognizable. Sometimes turning the background to pure abstractions is a good thing, but, many clients will actually want to be able to recognize the location they selected for their shoot! And while the 28mm equivalent widest angle might not be the widest lens out there by a wide margin, there’s very little body image distortion at the 17mm focal length, even when the subject is very close to the edge of the frame and near the camera. Serious subject distortion may work well for skateboard action shots, but when there’s brides involved, not so much!
The Sigma 17-50mm F2.8 EX DC OS HSM is a top-quality tool for working pros, as well as enthusiasts who demand the utmost in image quality in a fast standard zoom lens.
The Sigma 17-50mm F2.8 EX DC OS HSM is also a fantastic lens for landscape and documentary photography, too! Check out the fantastic images Sigma Pro David Fitzsimmons created with this fast standard zoom in this Lens Exploration blog posting.
Originally Posted on: http://blog.sigmaphoto.com/2012/why-upgrading-to-the-sigma-17-50mmf2-8-ex-dc-os-hsm-is-a-wise-business-decision/