Pentax Program Plus - Infrared Index Mark

INFRARED INDEX MARK
If you intend to take infrared photographs using
infrared film and R2 or 02 filters, it is necessary
to compensate for the difference between visible
light focus and infrared focus. As shown on the
left, note the subject-to-camera distance on the lens
distance scale as you focus through the viewfinder
and turn the focusing ring until that distance setting
aligns with the red infrared index mark. The figure
shows an example in which the subject-to-camera
distance is set at infinity ( « ).
As for exposure control required in infrared
photography, refer to the instructions contained in
the film package.