The Zeiss Loxia 2/50 ($949) is one of the first in a new series of manual focus lenses for Sony full-frame mirrorless cameras. The companies have collaborated on optics before, including the excellent autofocus Sonnar T* FE 55mm F1.8 ZA ($998.00 at Amazon) , another lens for full-frame Sony cameras. The Loxia is just as good from an optical standpoint, a little less expensive, and offers a much more pleasant manual focus experience. The Sonnar 55mm is one of our favorite lenses, and earned Editors' Choice honors when we reviewed it. The Loxia is every bit as good, and is also worthy of being called Editors' Choice.

At 2.3 by 2.4 inches (HD) the Loxia is quite compact. It is a bit heavy at 11.3 ounces, but that's due to its all-metal construction. Like the Loxia 2/35 ($1,299.00 at Amazon) , this 50mm version supports 52mm front filters; Zeiss promises to keep that filter size consistent with future lenses in the series as well. The lens is purely mechanical in operation, but it does transmit EXIF data to the camera, recording the set aperture and focal length in each image. The lens mount is sealed, so the weather-resistant design of the Alpha 7 cameras with which it is compatible is preserved.

The manual focus action is purely mechanical, and the focus throw is long. The focus ring turns a full 180° to go from the minimum 0.45-meter focus distance to infinity. When shooting at a wide aperture, the long, precise focus throw allows for excellent control over depth of field. The focus action is smooth and consistent; it's not loose to the point where you'll turn it accidentally, nor is it too tight to turn comfortably. The barrel has a printed depth-of-field scale with markings for f/4, f/8, f/16, and f/22.

The physical aperture ring can be set from f/2 through f/22 in third-stop increments. It's also possible to disable the aperture clicks; Zeiss includes a tool that turns a screw in the lens mount to switch to a free-moving diaphragm, which is preferable for video work. There's no optical stabilization, which is beneficial for shooting handheld video, but if you pair the lens with the Alpha 7 II ($898.00 at Amazon) the lens will benefit from in-body image stabilization.

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I used Imatest to check the sharpness of the Loxia when paired with the 24-megapixel Alpha 7 II. At f/2 the Loxia scores 2,635 lines per picture height on a center-weighted sharpness test. That's better than the 1,800 lines we used to consider an image sharp. Performance is even across the entirety of the frame; even the periphery of the frame resolves 2,454 lines. Narrowing the aperture improves performance—at f/2.8 the lens manages 2,745 lines, it improves to 2,804 lines at f/4, and it peaks at 2,946 lines at f/5.6.

Diffraction sets in at f/8, robbing the lens of some resolution, but even there it shows 2,858 lines. At f/11 it scores 2,794 lines and it's still at 2,700 lines at f/16. It's not until you get to f/22 that there's a noticeable dip in clarity—the Loxia shows about 2,300 lines there. Barrel distortion is modest, about 1.6 percent, which is just noticeable in field conditions. It gives straight lines a slight outward curve, but it's easily remedied via software.

The Zeiss Loxia 2/50 is a lens with very few flaws. It's sharp from edge to edge, even at its widest aperture, and shows just a minor amount of barrel distortion. It's equally capable for stills and video, and its mechanical focus system offers the tactile feel that the focus-by-wire systems of many modern autofocus lenses lack. If you're primarily an autofocus photographer, the Sony Zeiss Sonnar T* FE 55mm F1.8 ZA is probably a better fit for you, and it's just $50 more expensive. But if you prefer the feel of a purely mechanical lens, the Loxia is a terrific alternative. Both Zeiss lenses are optically excellent, and both earn Editors' Choice honors.

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