Leica's f/2 Summicron lenses have traditionally delivered excellent performance at a reasonable (for Leica) price tag. The Summicron-M 50mm f/2 sells for a mere $2,295, and even the current version has been on the market for enough time so that used examples are available for much less. So why does the new Leica APO-Summicron-M 50mm f/2 ASPH. ($7,195 list) cost more than three times as much? Quite simply, it's as close to perfect as any that I've shot with. It's sharp from edge-to-edge, even at f/2, shows no distortion, and is completely free of chromatic aberration. It's very expensive, and chances are that you don't need a perfect lens for your camera, but we're awarding it an Editors' Choice award based on its exemplary performance.

Like most rangefinder lenses, the APO-Summicron-M is quite small. It measures just 1.9 by 2.1 inches (HD), but is a bit heavy at 10.6 ounces. Its density is in part due to its all-metal construction, but you can't discount the heft of the glass—there are eight internal lens elements, arranged in five groups. The front element is fairly small in diameter, allowing you to use 39mm screw-in filters as needed. Like most rangefinder lenses, the close focus capability is limited to 0.7 meters. Aperture ranges from f/2 down to f/16 in half-stop clicks, and there are 11 aperture blades. There's a notch on the lens barrel to aid in focus adjustment, a physical aperture ring, and a telescoping hood. The lens ships with a slip-on metal cap with a soft, black felt lining.

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I used Imatest to check the performance of the lens when paired with the full-frame M (Typ 240). Its performance is, to put it lightly, impressive. We consider an image to be sharp if it manages to resolve more than 1,800 lines per picture height using a center-weighted analysis of our SFRPlus test chart. The Apo-Summicron records 2,788 lines at f/2, with sharpness that is even from edge to edge. Stopping down to f/2.8 improves its score to 3,496 lines, and it peaks at 3,843 lines at f/4. There's absolutely no distortion, and the apochromatic design means that you won't see any purple or green fringes at areas of high contrast or bokeh. To compare, the excellent Leica Summilux-M 50mm f/1.4 ASPH. managed to record about 2,300 lines at f/2, and the best performance we were able to muster was at f/8—3,680 lines. We tested that lens with the M Monochrom, a camera that benefits from an inherent advantage in sharpness due to the lack of a color filter.

If you want the absolute best 50mm lens that money can buy, the Leica APO-Summicron-M f/2 ASPH. is it. That kind of performance comes at a cost that not many are willing or able to pay. The lens is impressively small, but extremely well built. I'm not sure if I'd call anything perfect, but the APO-Summicron comes close. We're rewarding its design with a rare 5-star rating and our Editors' Choice award. Thanks to its cost, it's not a lens that many will get to shoot with, but those who do get the opportunity will undoubtedly walk away happy with the resulting images.