The Leica Summarit-S 35mm f/2.5 ASPH. ($7,250) is a must-have lens for Leica S system owners who prefer capturing images with a wide field of view. When paired with the large sensor of the S-E (Typ 006) ($3,999.00 at Amazon) and other S bodies, the Summarit records images with a field of view that's equivalent to a 28mm prime on a 35mm full-frame camera system, and it does so with a maximum f/2.5 aperture and minimal distortion. It's expensive—that's par for the course with both medium format photography and Leica—but its performance more than lives up to its price tag. It's a phenomenal lens that's worthy of being called our Editors' Choice.

But you don't get that type of image quality and sensor coverage out of a lightweight lens. The Summarit-S  measures 4.8 by 3.5 inches (HD) and is heavy at 2.1 pounds. Its 82mm front filter size is the same as several other S lenses, including the Summarit-S 70mm f/2.5 ASPH. ($2,499.00 at Amazon) , and its dust-proof and splash-proof design allows you to use it in all types of weather. The minimum focus distance is 21.7 inches (0.55-meter); you're not going to venture into macro territory with a wide lens, but it allows you to get pretty close to a subject and still capture quite a bit of the landscape behind it. The lens does have a depth-of-field indicator that changes as focus is adjusted, but there are no markings aside from the center point for f/2.5. Photographers who are used to using scale focus with wide-angle lenses at narrow apertures will likely miss that feature.

The standard version of the lens relies on the focal plane shutter of the S camera with which it is paired, which limits the maximum flash sync speed to 1/125-second. Leica also sells a version of the lens with a central leaf shutter and identical optics, the Summarit-S 35mm f/2.5 ASPH. CS ($8,450), which allows you to sync at speeds as short as 1/1,000-second.

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I used Imatest to check the sharpness of the Summarit when paired with the 37.5-megapixel S-E (Typ 006). At f/2.5 the lens scores 3,273 lines per picture height on a center-weighted sharpness test. That's well in excess of the 1,800 lines we like to see from a photo, and even the very outer edges of the frame are crisp at 3,000 lines. Stopping down to f/4 improves the average score to 3,515 lines, and it's shaper still at f/8 (3,808 lines) and f/8 (3,828 lines). Diffraction robs some image quality at narrower apertures—the score drops to 3,603 lines at f/11, 3,113 lines at f/16, and 2,292 lines at f/22, but you should feel comfortable shooting all the way down to f/16 with a minimal drop-off in image quality. There's a little bit of barrel distortion, about 1.6 percent, but that's not a lot for a wide-angle design, and it's easily remedied with a 1-click correction in Lightroom.

Simply put, the Leica Summarit-S 35mm f/2.5 ASPH. is a standout lens from a company that has built its reputation on top-notch optics. I'd have been happy if Leica had designed a lens that was this sharp and this wide, or was this wide and captured this much light, but doing all three at once is a feat. If you're a wide-angle shooter, especially one that feels at home with the 28mm-equivalent angle of view that this lens produces, the Summarit-S 35mm is good enough that you should consider the S system just to shoot with it. That's just about the strongest recommendation I can give to any lens, and it's why we're calling this one our Editors' Choice.

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