No compromise on quality

The author checks out Sigma's new 18-35mm f/1.8 lens, which is compact, functional and affordable

Buying an off-brand lens was always a good way to save money, but not often a good way to improve your photographs. Bargain lenses used to regularly compromise picture quality.

But now some third-party lenses are on a par with the products from the big-name manufacturers. Case in point: Sigma's new 18-35mm f/1.8 zoom lens. It takes in more light than zooms from Canon or Nikon and doesn't compromise on sharpness. That makes it a go-to lens for hand-held shooting in low light.

I tried taking candlelight photos of a Thanksgiving table setting at dusk, a shot I wouldn't normally try without a tripod. Shooting hand-held, I was still able to get an impressively sharp image.

Some people have reported problems getting the lens to focus accurately, but this lens is part of the Global Vision series, which means with a $60 dock, you can hook the lens to a computer and use free Sigma software to fine-tune the focus.

I had a different focus problem. While still shots were fine, it was difficult to get consistent focus on a fast-moving puppy playing fetch. That could be an issue with either the speed or the consistency of the autofocus - I couldn't tell which. I worked around the problem by using burst mode to take several sequential shots.

Although the lens is a zoom, it has a fairly small range. The lens is not for full-frame cameras, so the effective length of the lens is approximately 27-52mm. That is a modest wide angle to what used to be called a "normal" lens, because it is supposed to capture a perspective similar to that seen by the human eye. You won't be using it for concert shots unless you are allowed onstage.

At $800, the Sigma is relatively low-priced. To put it in perspective, at B&H Photo online, the Canon EF 16-35mm f/2.8 lists for $1,700, and the Nikon 17-55mm f/2.8G ED-IF AF-S DX lists for $1,400.

Sure, for that same $800 you could alternately buy two or three fast, non-zoom lenses that cover the same range, but you'd have a lot more to carry.

© 2013 The New York Times