9
the lenses are provided either with click- stop
diaphragms, with a device for preselecting the
desired diaphragm setting or with completely
automatic pressure or spring diaphragms.
Operating the click-stop diaphragm on
the Jena T f2.8/50 mm lens (Fig. 6) and
the Trioplan f2,9/50 mm :
Upon moving the
diaphragm setting ring of these lenses, it will
be felt to engage gently to each marking on the
aperture scale. When turning the diaphragm
setting ring to stop down the lens, it is merely
necessary to count up to the previously-deter-
mined number of click stops in order to select
the desired aperture. ln this way it is not neces-
sary to take the camera away from your eye.
Operating the pre-set diaphragm mecha-
Fig. 6
Fig. 7
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