ExpoImaging ExpoAperture2 Manual (Imperial/Standard) - Manual (Page 4)

ExpoAperture 2 Depth-of-Field Guide Manual
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1. - An Introduction to Depth-Of-Field
"There is nothing wrong with your television set. Do not attempt to adjust
the picture… We can reduce the focus to a soft blur, or sharpen it to crystal
clarity..."
The Outer Limits
Opening narration, The Control Voice, 1963-1965
The human eye is marvelously flexible and adaptive. It can adjust its focus so rapidly that
the impression is given that its entire field of view is in sharp focus when only a small
portion is actually in focus at any one time.
A camera lens, in contrast, freezes the focus on the image plane the instant the shutter is
released, preserving forever whatever the lens has rendered in or out of sharp focus. A
viewer of a photograph can immediately discern the different areas that are in sharp focus
and those that are not.
The distance between the nearest and furthest points from the camera at which everything
appears sharp is termed the depth-of-field. In many types of photography, such as
landscape photography, it is desirable to have the entire image as sharp as possible. In this
case the photographer may focus on the hyperfocal distance to obtain the maximum depth-
of-field possible. In others, the creative use of depth-of-field can be used to isolate elements
that the photographer may wish to emphasis or deemphasize. This opens the photographer
to the possibility of using selective focus (the ability of lenses to render some objects within
a scene in focus while others appear out of focus), as a compositional tool.
1.A. - Focus as a Compositional Tool
All photographers know that they need to focus their cameras, but only skilled
photographers know how to use selective focus as a compositional tool. Selective focus can
be used compositionally in two ways, to direct attention to the subject, and to eliminate
distractions.
Directing attention – In a photograph, a viewer's eye is irresistibly drawn to the area of sharpest
focus. It follows that a photographer who can control focus can also control the viewer's
attention. Sharp focus implies that the photographer is placing emphasis on an area for a
specific reason. In addition, elements that are in sharp focus are united by their similarity,
which separates them from the other out-of-focus elements. Consequently, the creative use
of focus can help build and support visual relationships.
Eliminating distractions – Often, either the foreground or background elements of a scene
detract from the main subject, directing the viewer's eye away from the photograph's center
of interest. When such areas are purposefully thrown out-of-focus, they are less likely to
distract the viewer. In some cases, a slight softness is all that is necessary. In other cases,
the effect may need to be exaggerated. The photographer needs to make the appropriate
compositional decisions based on the circumstances and his or her intent.