Leica M3 Instructions Manual page 10

The Depth-ol-Field Scale
The lens reproduces sharpest those parts of the scene which are at the exact distance
- in a plane parallel to the film - on which it is focused. This maximum sharpness
gradually falls off in front of, and behind, the focused distance, resulting in a certain
zo ne w ithin w hich everything is still acceptably sharp. The extent of this zone of
sharpn ess - . l he " dept h-of-field " - depend s on th e subiect d istance, the focal length of
t he lens, and the aperture. Stopping down increases the sharp field, which is desirable
f o r mosT subiects extending appreciably in depth .
To find the limits of this zone, look at the depth of field scale of your lens. The sharp
zone is that enclosed between two index lines of the same aperture number. If, for
instance, you have set your 50 mm
SUMMICRON lens to 15 feet, the
avai lable depth-of-f ield with an
aperture of f /4 (see red arrows in
th e illustration ) extends from about
12 V2
to 20 feet. If, however, you
sto p down to f il l , the zone o f
sharpness cove rs a field from a bout
9 to 40 feei·. When altering th e
aperture, be sure to adiusl' the ex-
po sure time according.ly.
Soc also page 9, O;>l ical Depth·ol· fi eld
In:licaror in th:J measuring f ield or the (on"'l·
bined ran ge-v ie wfin der.
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