The Samsung 50-200mm F4-5.6 ED OIS III NX ($349.99 list) is a telephoto zoom lens for Samsung NX mirrorless cameras. When paired with the APS-C NX sensor it covers the same field of view range as 75-300mm would on a 35mm or full-frame digital camera. It's the perfect complement to the standard 20-50mmSEE IT or 18-55mmSee it at Amazon UK zoom that ships with NX cameras. There isn't a pro level f/2.8 telezoom available for the NX system at this time, so if you want a telezoom, this is your only option. Thankfully it's a good one, and it won't break the bank.

The lens itself is 4 by 2.8 inches (HD) when set to 50mm, and it weighs about 14.3 ounces. It extends while zooming, and there's also a reversible hood included that adds a couple inches to the height. Micro Four Thirds shooters have some more compact options for zoom lenses, as the smaller sensors in those cameras don't need as much glass to cover the image circle. The Olympus M.Zuiko 40-150mm (80-300mm equivalent) is only 3.3 by 2.5 inches in size and weighs just 6.7 ounces.

The zoom action is smooth, and the front element doesn't rotate during zoom or focus; it supports 52mm filters. The zoom ring occupies most of the barrel, but there's also a manual focus ring just behind the front element. The lens supports Samsung's iFn system, so the focus ring can also be used to adjust camera settings when used in conjunction with the iFn button, found towards the base of the lens. There's also a toggle switch to change between manual and autofocus operation. The minimum focus distance is just about 3 feet, regardless of the focal length.

I used Imatest to check the sharpness of the lens when paired with the Samsung NX2000. At its widest angle and aperture the lens performs superbly, netting a center-weighted score of 2,528 lines per picture height. That's better than the 1,800 lines we require for a photo to be called sharp, and that sharpness is also there at the edges of the frame; it manages an impressive 2,144 lines there. Stopping down to f/5.6 improves sharpness to 2,686 lines and edges near 2,300 lines. There's a little bit of distortion evident here, about 1 percent, but it's not worth writing home about.

Zooming to about the midpoint of the range, 130mm, narrows the maximum aperture to f/5. Sharpness is still very good here, 2,246 lines, but edge performance is a bit soft at 1,603 lines. Stopping down to f/8 improves the average sharpness only slightly, but the edges improve to 1,745 lines. At 200mm the lens maxes out at f/5.6 and sharpness dips down to 1,805 lines. The center is tack sharp, but the midpoint and edges of the frame aren't quite as impressive at only 1,600 lines. Stopping down to f/8 improves things a bit, bringing the edges up to 1,630 lines and the midpoint of the frame to a more respectable 1,679 lines.

If you're in want of a telephoto zoom lens for your NX camera, this is the one to get for a couple of reasons. It's the only one currently available for the system, although you can certainly use a lens adapter to mount one made for an SLR and manually focus. But it's also a good lens, albeit one with a slower aperture. The optical stabilization system makes it possible to get a steady handheld shot when zoomed in, even when stopped down to f/8. The f/4-5.6 aperture can't keep pace with the pro f/2.8 zoom lenses that SLR shooters have access to. But those lenses are many times more expensive and generally much larger and heavier than this one. There are some issues with sharpness when zoomed all the way in. Even at f/8 there's a touch of softness as you more away from the edge of the frame, but it's not dull to the point where you're going to notice it in smaller prints.