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Reproduced for Historical & Reference purposes by Paul M. Provencher -
http://whitemetal.com
11
Bright field focusing
1 You can start viewing and focusing before
and after cocking the rapid wind lever. When
the automatic preview lever is in the "AUTO"
(automatic) position, the meter is at "OFF",
the diaphragm is fully open except for the
moment of exposure.
2 Turn the distance scale ring until your
subject image is clearly in focus. It is not
always necessary for you to view and focus
with the diaphragm fully open. In bright
sunlight, you can easily focus with the
diaphragm closed to f/5.6 or f/8 and still
observe the depth of field. It is easier,
however, to focus with the diaphragm fully
open as your subject image is much brighter.
When the letters "MAN" appears beside the
lever, the lens is in manual position; when
"AUTO" appears, it is in the automatic
position.
Microprism
Asahi Pentax cameras have a Fresnel lens
with a microprism center underneath the
ground glass. As you look through the
finder, you will see that the Fresnel lens
consists of many concentric rings which
provide the brightest possible image on the
ground glass.
The microprism is the center portion of this
diagram. When your subject is in focus, the
image in the microprism will be sharp and
perfectly clear. If your subject is not in
focus, the microprism will break the image up
into many small dots, much like and
engraver's screen. You can focus your
subject on any portion of the ground glass.