The Carl Zeiss C Biogon T* 2,8/35 ZM ($860 list)($749.00 at Amazon) is a super-small 35mm lens for M-mount rangefinder cameras. Despite being priced on the budget end of the Zeiss spectrum, it retains the top-end build quality and actually betters the other lenses in the ZM series in terms of image sharpness. It's an easy pick for our Editors' Choice award, and if you're a rangefinder shooter of want of a 35mm lens it's a good one to get. Of course, it can also be used on mirrorless cameras, including the full-frame Sony Alpha 7R($629.99 at Amazon) and the Micro Four Thirds Olympus OM-D E-M5($499.00 at Amazon) via a simple mechanical adapter.

The lens measures just 2.2 by 2 inches (HD), weighs 7.1 ounces, and supports 43mm front filters. There's a metal lens hood available from Zeiss for $84. The closest Leica lens in terms of focal length and aperture is the 35mm Summarit-M f/2.5 ($1,950); it's a bit smaller at 1.3 by 2 inches, and despite its high asking price it also omits a hood. (And the add-on hood for the Leica is priced at $130.) Like most rangefinder lenses, the C Biogon has a minimum focus distance of 0.7-meter.

The C Biogon maintains the exquisite build quality shared by the other lenses in the ZM series. Its barrel is metal, its focus ring is tight with smooth operation, and its aperture ring can adjusts from f/2.8 through f/22 in third-stop increments. There's a small nub on the  focusing ring that makes it easy to adjust using a finger; it's not as large as the similar protrusion found on modern Leica lenses, but it gets the job done. There's a depth of field scale printed on the lens with full-stop markings from f/4 through f/22.

I used Imatest to check the performance of the lens when paired with the full-frame Leica M (Typ 240)($2,969.00 at Amazon). It's incredibly sharp at every tested aperture, and shows absolutely no distortion. At f/2.8 it already scores 2,955 lines per picture height on our center-weighted sharpness test. That's better than the 1,800 lines required to call a photo sharp, and impressively the very edges of the images are extremely sharp at 2,268 lines. The Biogon T* 2/35 ZM doesn't deliver that level of performance until its aperture is narrowed to f/4.

At f/4 the C Biogon improves to a staggering 3,668 lines, and at f/5.6 its at its best at 3,764 lines. Resolution starts to drop due to diffraction, as you stop down from there, but even at f/11 it kisses the 3,000 line mark. Yes, the lens doesn't have the maximum f/2 aperture of its more expensive sibling, but if you're willing to live with an f/2.8 optic you'll be rewarded with images that are absolutely tack sharp.

There's a lot to like about the Carl Zeiss C Biogon T* 2,8/35 ZM—it's quite compact, extremely sharp from edge to edge, and is priced attractively (for a Zeiss lens). If you're in want of an M-mount 35mm lens with a wider aperture, but don't want to spend the extra money for the Biogon T* 2/35, there are some alternatives available from Voigtlander. These include the compact Color-Skopar 35mm f/2.5 ($409) and the Nokton 35mm f/1.4 ($629). We haven't tested these as of yet to see how they stack up against the C Biogon, but Voigtlander lenses are generally well built and deliver good—but not off the charts—performance. As it stands the C Biogon earns our Editors' Choice award; it's an excellent 35mm lens for rangefinder and mirrorless camera shooters alike.

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