Leica SUMMARIT-S 1:2.5/70mm ASPH Instructions Manual page 16

For focusing, the entire optical system is moved - with the exception of the fixed front filter
- which means that the total length of the lens remains the same. To improve the imaging
performance with the close up setting, the rear assembly made up of an aspherical lens and a
lens with negative refraction is moved independently. This „floating element" reduces spheri-
cal aberration, coma and distortion and ensures a uniform per formance at all distances.
Summary: The LEICA SUMMARIT-S 70 mm f/2.5 ASPH provides exceptional imaging
per formance from the infinity setting to the close-up range, at full stop and when stopped
down. This outstanding performance right up the maximum close-up range gives the photo-
grapher a unique choice of compositional options without having to accept any compromises
in image quality.
Design of Leica S lenses
In principle, all Leica S lenses have the same design: There is an external bayonet (2b) for the
lens hood (1) and an internal thread (2a) for filters on the front mount, a setting ring for the
distance (3), a window (4) for reading the distance scale (4a) underneath and a fixed ring (5)
with a red alignment button for changing lens (5a).
In the bayonet flange there is a contact strip (6), which is used to transfer all data between
the camera and the lens, including the control commands for autofocus, the diaphragm and, if
present, the central shutter.
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