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Selective focus in camera photography is simply another
application of depth of field. It uses the same principles and
techniques as zone focusing for camera photography, but its objectives are different. With
zone focusing a photographer is usually striving for as much depth of
field as possible in keeping with the subject and lighting conditions.
The aim is to avoid unnecessary focusing. However, with selective focus
the goal is not to eliminate focusing, but to compress depth of field
to a point where the subject will stand out sharply against a soft
background. This is to control depth of field of photography in order
to make the subjects stand out.
A situation calling for selective focus might be one in which you are
taking an outdoors portrait of someone. No matter where you place your
subject, the background is harsh, full of detail and distracting. You
want your subject to be clear and sharp, but the background would be
far less disturbing if it were somewhat out of focus. How can you
accomplish this? you may turn to depth of field scale on your lens to
determine e the zone focusing limits, and then keep the background well
beyond the farthest point. However, there is a faster, more direct
method of controlling selective focus by simply observing the subject
and background through the camera's viewfinder at the taking aperture
and then making any necessary changes until you arrive at the effect
you want. As you already know,, a longer focal length lens, a larger
f-stop or a closer camera to subject distance will reduce depth of
field. Since reduced depth is what you are after, use any or all of
these devices to throw the background into a soft blur.
If you have a longer lens available, try that first, a 135mm lens used
at the same aperture and distance as a 50mm lens, for example, limits
depth of field considerably. Just the change of lenses may throw the
background out of focus enough to let the subject stand out clearly. If
the difference in sharpness between subject and background is still not
enough, use the longer lens at, or close to, its widest aperture. If an
even more pronounced effect is wanted, move closer to your subject and
compose a "tighter" portrait as well. You certainly should have no
trouble with a distracting background now unless there are bright, out
of focus highlights still competing for attention; a change of camera
angle should solve this problem.
If a longer lens is unavailable, use what you have at a very wide
aperture coupled with a short lens to subject distance. Remember when
observing the effect of selective focus in the viewfinder to always do
it with the lens stopped down to the aperture you expect to use. There
is a stop down lever or button on most lenses to allow for this. if
your lens is at its normal, fully opened aperture and you don't realize
it, focus may look just righ tin the viewfinder, but the final picture
may be disappointment.
If the light on your outdoor subject is too bright to allow a large
aperture, move into the shade. The soft effect of shaded,
non-directional lighting is more flattering anyway. Indoors, unless you
use flash, portraits taken against distracting walls and furnishing
shouldn't present the problem of too much light, so wide apertures can
be selected as a matter of course.
Portraits of people aren't the only subjects that benefit from
selective focus. Pictures of pets are often taken outdoors where
fences, posts, and other background clutter spoil their portraits. Move
in close with a large aperture and see how much improvement you can
make in photographs of these popular subjects. Flowers and small art
objects are two other likely candidates for the selective focus
treatment. Keep the technique in mind at all times. It can helps a
great deal.
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