With an angle of view corresponding to that of a 28 mm lens in 35 mm format, the Leica Summarit-S 35 mm f/2.5ASPH. can be used as a universal wide-angle lens with characteristically dramatic perspectives. At the same time,its unusually fast initial aperture offers fascinating creative potential for the use of selective focusing to isolate subjects from their surroundings. The alternative CS version with a central shutter and a close focusing limit of only 55 cm (~1.8 ft), offers extreme versatility for a wide range of photographic needs.
The combination of a fast initial aperture and a wide angle of view are only possible by the investment of enormous effort in the design and construction of such a lens. And here, Leica employs the benefits of numerous years of experience gained in the production of lenses with aspherical surfaces, a feature very rarely found in such large diameter lenses. In the front group, a lens with an aspherical surface created in an immensely precise grinding and polishing process guarantees extremely low distortion, and a further aspherical surface is employed in the rear groups. Altogether, five of the eleven lenses arranged in nine groups are manufactured from glass with anomalous partial dispersion, and three are fluoride lenses with particularly low dispersion (color scattering) characteristics.Rear group focusing in this splash-proof and dust sealed lens ensures consistent imaging performance from infinity to the closest focusing distances and a constant length when focusing.
Thanks to this special construction, the image performance of the Summarit-S 35 mm f/2.5 ASPH., is exceptionally good wide open and can be improved only very slightly in the corners of images by stopping down. A vignetting value of just 1.4 stops, and distortion no greater than 1.7 %, even at its closest focusing limit, are imperceptible in practical use. The outcome of the enormous effort invested in the design and construction of this lens is a wide angle lens that allows photographers to fully exploit its creative opportunities without compromise.