Focusing and Depth of Field
On the focusing ring are the distance scales and a
knurled rubber grip which is closest to the camera
body. You focus the lens by rotating the focusing ring
until you obtain a sharp image of the subject in the
viewnder.
Thedistancebetweenthesubjectandthelmplane
isreadothefocusingring’sdistancescaleopposite
the central lens index. The distance in meters is shown
in white numerals, and the distance in feet is in orange
numerals.
Objectscloserorfurtherawaythantheselecteddis-
tance will be sharp, within certain limits. The limits of
thiseldof sharp focus,i.e. depthofeld,varywith
the aperture.
Thedepthofeldavailableatanygivenf/stopcanbe
readothedepth-of-eldscaleonbothsidesofthe
central index. The rings on the illustration indicate how
toreadthedepthofeldscalewithanapertureof11
lnfrared Photography
lnfrared (IR) rays (wavelengths longer than 800 nano-
meters) are refracted to a focal plane somewhat be-
hind the focal plane of the visible light images formed
on the focusing screen. To compensate for this dis-
crepancy,proceedasfollows:
Focus as usual on the focusing screen. Then rotate
the focusing ring until the distance set is opposite the
red IR index.
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