Leica Noctilux-M 75 f/1.25 ASPH Manual Del Usuario página 19

EN
DESIGN OF LEICA M LENSES
In principle, all Leica M lenses have the same external design: an aperture
setting ring (4), a focusing ring (5), a fixed ring (6) with an index for focusing (6a),
a depth of field scale (6b), and a red alignment button for lens change (6c).
Furthermore, the ring on this lens has a tripod thread and a fitting groove to
attach the tripod adapter (see p. 23).
A 6 bit lens identification bar code (7) is situated on the bayonet flange. It relays
lens data to the camera body so the exposure metering system of digital Leica M
models can be calibrated. The information is also used to custom-optimize image
data according to the respective lens.
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