Exakta RTL 1000 - Page 20

Focusing with focusing system
(Fresnel screen) :
Image-
brightening
Fresnel screen
Circular mark
Pointer of mea-
suring device
Annular field in
the ground-
glass screen
Microprism
The EXAKTA RTl 1000 may aptianally be supplied
with a focusing system in all its viewfinder units.
With this focusing system, a sharp image is mainly
obtained using the annular field in the ground-
glass screen (far moving subjects, phatographs
taken with a magnifier, and photomicrographs).
To increase the accuracy of focusing or in case of
slowly moving and stationary subjects focusing
is performed by means of a microprism field. In
case of incorrect focusing the microprism field will
show an image which in blurred to a greater
degree (the blurred image "flickers") . The lens
will be correctly focused when the image in the
microprism is at its sharpest (i. e. no flicker effect).
It is however. absolutely necessary to focus with
a large diaphragm opening (small aperture
number) (this is important above all in case of
lenses without internal release). With apertures