Film Plane Indicator; Distance Scale; Infrared Index Mark - Canon A-1 Instructions Manual

Film Plane Indicator
This mark is engrnved on the top of the
camera beside the film rewind knob, j us l to
the left of the pentaprism, to indicate the
exact position o f Lhe film plane. IL is no l
used in general photography, but it is helpful
in dose-up photography and photomacro-
graphy for obtaining the exact shooting
distance from film to subject.
Distance Scale
The distances on the scale are calibrated
from the film plane to indicate the focused
distance from film plane to subject.
The scale is not generally used except
when confirming depth of field, perfor-
ming guide n umber calculations in flash
photography, or using infrared film.
Read one-digit distances in the middle o f Lhe
number marked on the scale. Two-digit
distances should b e read at the point b e-
t ween the two digits.
-75-
Infrared Index Mark
Since infrared light rays have longer wave-
lengths which fo cus on a plane slightly
b ehind tha t of ordinary visible light rays, it
is necessary to slightly adjus t the focus of
the lens when using b lack and white infrar ed
film . The infrared index mark engraved on
the lens barrel is used for th is purpose. After
focusing the same as usual, note the tiny red
dot engraved on t h e le ns barrel just to the
righ t of the distance index, and turn th e
focusing ring to al ign the foc used distance
with this red do t . For ins tance , if t he fo cus
is at 5m on the distance scale, turn the
focusing ring to align the 5m mark w ith the
red dot. After that focusing correction, you
can release the shutter .
When using infrared b lack and white film,
visible light rays must be kep t out by mea ns
o f a deep red fi lter (Rl) over th e le ns. When
using infrared color film, there is no need to