|Sigma 28-70mm f2.8 EX Pro
by Vivid Light Staff
This lens put on quite a few miles with us before going back to Sigma, accompanying us to the Chesapeake, Assateague, Atlantic City, on a portrait shoot, and finally into the urban wilds of Philadelphia before we finally relinquished it.
28-70mm is the most popular zoom focal range, and the focal range most often included with packaged SLRs. But most of the those lenses are consumer quality, yielding decent but not stellar images. When folks are ready to step up to higher quality gear, they start looking at lenses with sharper optics and larger maximum apertures. This lens is Sigma's answer for those photographers.
The first thing you'll notice if you've been using lenses with maximum apertures in the f3.5-5.6 range is how much brighter your finder image will be when using an f2.8 lens. You're letting in a lot more light and it can feel like you're using a whole new camera.
The next thing you'll notice if stepping up from a consumer lens is the weight. At almost one and a half pounds this lens is significantly heavier than the 28-80mm lenses bundled in most camera kits. And that's a good thing. The weight comes from the high quality glass contained in this lens including two aspherical elements in the front and rear lens groups.
This lens also feels a bit "front heavy" when compared to similar lenses from other manufacturers, particularly when used with a light camera body. This tendency would be far more noticeable with an N80 for example than with an F100. It's all a matter of balance. It didn't affect the usefulness of the lens, it just feels a bit unusual until you get used to it.
One problem we found in using the lens was it's aperture ring. Our sample was a Nikon mount lens. Nikon lenses still have an aperture ring, allowing you to set the lens aperture on the lens rather than through a dial on the body (though newer Nikon camera bodies support this method as well). The problem was that the aperture ring seemed to be an afterthought in the lens design. Most lenses made for Nikons taper in to the aperture ring providing plenty of room for your fingers to grip the ring. However on this lens there was no taper and almost no room to get to the aperture ring with your fingers. The best technique we found for manipulating the aperture ring was to press the side of one finger against the ring and click it forward or backward. We got used to doing it this way after a while, but it always felt awkward. Canon, Sigma, Minolta, and Pentax users won't have this problem.
The lens is also bundled with what Sigma refers to as their Perfect Hood (shown above). Use of this hood is made possible by Sigma's use of a helical focusing system that does not rotate the front lens element. This is a god send for anyone using polarizers or split neutral density filters. Just be aware that you won't be using the hood when using those filters. Also be aware that stacking filters may cause some slight vignetting at 28mm, as you would expect.
The lens mount is metal, as you would expect from a pro lens. The general construction is heavy and solid, again, as you would expect from a lens in this class, and the common 77mm filter size means that your current crop of filters will work with this lens (assuming you already own others in it's class). When focusing manually we found the action of the lens to be smooth and well damped with a reasonably short throw from minimum focus distance to infinity.
But the real story with any lens is the quality of it's images - which we found to be excellent. All images were uniformly sharp and contrasty, including those shot at f2.8. We didn't experience any flare problems whether using the lens hood or not.
As a benchmark we shot this lens against a Nikon 35-70mm f2.8. Looking at the slides on a light table with a 22x loupe, the Nikon appeared to have a slight edge in sharpness, but at double the price.
With street prices hovering around $300, this lens is a very good buy when priced out against 28-70mm f2.8 OEM lenses from Nikon, Canon, Minolta, and Pentax, all of which are over $1,000. However this isn't a Sigma HSM (Hypersonic Motor) lens, whose fast focus would put it on a truly level playing field with all of those competitors. The lens gives up a slight edge in sharpness to the Nikkor we benchmarked it against, but considering the price differential this is a lens you should definitely consider when looking at lenses in this focal range.
28-70mm is the most popular zoom focal range
But the real story with any lens is the quality of it's images
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