Pentax 645 - Infrared Index Mark

INFRARED INDEX MARK
1. Adjust the distance scale (set at the "in-focus" point). 2. Then move to the red infrared index mark.
In the taking of infrared photographs using infrared
film and R2 or 02 filter, it will be necessary to
compensate for the difference between the visible
light and infrared light focus.
As illustrated, read the camera-to-subject distance
on the distance scale of the lens while focusing
through the viewfinder; turn the focusing ring until
the distance setting aligns with the red infrared
index marking (red line). The picture shows an
example where the camera-to-subject distance is set
at infinity (oo).
For exposure control required in infrared
photography, refer to the instructions contained
in the film package.
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