Minolta XG-M - Page 19

FOCUSING
33
The focusing screen of your XG-IVl features
a split-image spot surrounded by a band of
microprisms in the center of an acute matte
field.
To focus the camera visually with usual
lenses, look through the viewfinder with lens at
full aperture and turn the focusing collar on the
lens until the upper and lower subject Images in
the spot are exactly aligned with no broken
lines between them and/or the subject image in
the band does not shimmer or appear broken
up. At this point, the subject image within the
focusing aid should appear clearest and seem to
blend with that on the matte field around it.
Out of focus
Though the most satisfactory focusing aid
and method depend upon the condition^ and
personal preference of the photographer, the
above method may provide the best results with
medium wideangle to medium telephoto lenses.
Generally speaking, however, you will pro¬
bably find that using the split-image spot will
provide the easiest way to focus with subjects
having vertical lines; the microprism band for
lenses from medium wideangle through medium
telephoto, especially with subjects not having
vertical lines; and the matte field for longer
lenses or macro or other work involving con¬
siderable lens extension.
Subject in focus
34
Depth of field
The distance behind and in front of the
focused distance within which the image
appears acceptably sharp is called the depth of
field.
It extends a greater distance behind the
focused distance than in front and is deter¬
mined by three factors: the aperture size, the
distance at which the lens is focused, and the
focal length of the lens in use. Depth of field
increases as the lens is stopped down (e.g., f/2
to f/16) and becomes greater the farther from
the camera the lens is focused. It decreases as
the lens is opened up (e.g., f/16 to f/2) and the
closer to the camera the lens is focused. Depth
of field is greater for short focal length lenses
than for telephoto's at the same focused dis¬
tance and aperture. It is at its least for any
given lens in normal mounting when the lens is
at maximum aperture (as when metering and
focusing normally with Minolta MD- or
MC-type lenses) and at minimum focusing
distance. ^
l^-Focused distance—