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The nominal focal lengths of the Leica M lenses are based on the 35 mm-
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format, i.e. on a film format of 24 x 36 mm. In comparison, with its 18 x 27 mm,
the sensor in the digital Leica M 8 models is somewhat smaller though – by
a factor of 0.75. Therefore, when used on the Leica M 8 models, these lens-
es have angles of view corresponding to lenses with focal lengths that are
longer by a factor of 1.33 (1.33 = reciprocal of 0.75). This has the respec-
tive effects on their perspective, but not on their depth of field, which, with
the Leica M8 models, can also be read directly off the lens (see "Depth of
field scale", p. 16).
The 6 bit lens identification bar code (7) situated on the bayonet flange
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enables the digital Leica M models to identify the attached type of lens. This
information is utilized by the camera to optimize exposure and image data.
This is valid regardless of the format of the respective camera – be it
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18 x 27 mm (sensor size) as in the digital Leica M 8 models or 24 x 36 mm as
in all other Leica M models.
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