PERSPECTIVE
Perspective refers to the relationship of imaged objects in
a photograph. This includes their relative positions and sizes and the space
between them. In other words, perspective in the composition of a photograph is
the way real three-dimensional objects are pictured in a photograph that has a
two-dimensional plane. In photography, perspective is another illusion you use
to produce photographs of quality composition. When you are making pictures,
the camera always creates perspective. Because a camera automatically produces
perspective, many novice photographers believe there is no need to know much
about it. This attitude is far from correct. When you know the principles of
perspective and skillfully apply them, the photographs you produce show a good
rendition of the subject's form and shape, and the viewer is given the
sensation of volume, space, depth, and distance. Additionally, the photographer
can manipulate perspective to change the illusion of space and distance by
either expanding or compressing these factors, therefore providing a sense of
scale within the picture.
The human eye judges distance by the way elements within a
scene diminish in size, and the angle at which lines and planes converge. This
is called linear perspective. The distance between camera and subject and the
lens focal length are critical factors affecting linear perspective. This
perspective changes as the camera position or viewpoint changes. From a given
position, changing only the lens focal length, and not the camera position,
does not change the actual viewpoint, but may change the apparent viewpoint.
The use of different focal-length lenses in combination with
different lens-to-subject distances helps you alter linear perspective in your
pictures. When the focal length of the lens is changed but the lens-to-subject
distance remains unchanged, there is a change in the image size of the objects,
but no change in perspective. On the other hand, when the lens-to-subject
distance and lens focal length are both changed, the relationship between
objects is altered and perspective is changed. By using the right combination
of camera-to-subject distance and lens focal length, a photographer can create
a picture that looks deep or shallow. This feeling of depth or shallowness is
only an illusion, but it is an important compositional factor.
Using a short-focal-length lens from a close
camera-to-subject distance, or viewpoint, produces a picture with greater depth
(not to be confused with depth of field) than would be produced with a standard
lens. Conversely, using a long-focal-length lens from a more distant viewpoint
produces a picture with less apparent depth.
Rectilinear
Perspective
Most lenses produce rectilinear perspectives that are
typical of what the human eye sees. This is to say that lines that are straight
in the subject are reproduced straight in the picture. Most pictures are made
with rectilinear lenses.
Fisheye lenses and the lenses used on panoramic cameras
produce a false perspective. A panoramic lens produces panoramic or cylindrical
perspective. In other words, all straight horizontal lines at the lens axis
level are recorded as straight lines, and all other straight horizontal lines
either above or below the lens axis level are reproduced as curved lines. The
other false perspective is produced by a fisheye lens in which all straight
lines in the subject are imaged as curved lines toward the edges of the
picture.
Vanishing Point
Perspective
In vision, lines that are parallel to each other give the
sensation of meeting at vanishing points. When parallel lines, either
horizontal or vertical, are perpendicular to the lens axis, the vanishing
points are assumed to be at infinity. Other lines, those which are parallel to
the lens axis, and all other parallel lines at all other angles to the lens axis
meet at definable vanishing points. Thus lines that are parallel to the lens
axis, or nearly parallel, start in the front of the picture and meet at
vanishing points within the picture or at finite points outside the picture.
The place where the base of an object is located on the
ground in a picture is a clue to its distance from the camera viewpoint; for
example, in a landscape scene, the ground or ground plane rises toward the horizon.
The higher up in the ground area of the picture (up to the horizon) that the
base of an object is located, the further away it seems from the viewpoint and
the greater its height perspective.
Overlap Perspective
Another clue to distance in a photograph is overlap
perspective. When subjects within the picture are on about the same line of
sight, those objects closer to the camera viewpoint overlap more distant
objects and partially hide them. It is obvious to the viewer that the partially
obstructed object is behind the unobstructed object. This overlap is repeated
many times within the picture and gives the viewer a sense of depth and a
perception of the relative distance of objects.
Dwindling Size
Perspective
Through the experience of vision, you are aware of the size
of many common objects, such as people, trees, cars, buildings, and animals;
for example, you are aware that most adults are about 5 to 6 feet tall;
therefore, when two people are shown in a picture and one appears twice as tall
as the other, you cannot assume that one is in reality taller than the other.
Instead you assume the taller person is closer and the shorter person farther
away from the camera viewpoint. In this same manner, you make a size
relationship evaluation of all familiar objects. Thus you can make a distance
determination from this size relationship evaluation. The farther away an
object is from the viewpoint, the smaller it appears; therefore, when subjects
of familiar size are included in a photograph, they help to establish the scale
of the picture. Scale helps the viewer determine or visualize the actual size
or relative size of the objects in the picture.
Volume Perspective
When a subject is lit with very diffused light, the three-dimensional
form or volume of the subject is difficult to perceive because of the lack of
distinct shadows. If, on the other hand, subjects are lighted with strong
directional light from angles that cause part of the subject to be fully
lighted and other parts to be in shadow, a visual clue of the subject's form or
volume is provided When a number of such objects are included within the
picture area, the perception of form, volume, and depth is increased. When
front or side lighting is used, the length, depth, and shape of the shadows
cast on the ground provide a perspective of each object's volume. Also, the
distance between shadows cast on the ground helps you to perceive the overall
depth of the scene.
Atmospheric
Perspective:
For all practical purposes, air is transparent. For most
photography, this is fundamentally true; however, when pictures are made of
subjects at great distances, the air is actually less than fully transparent.
This is because air contains very fine particles of water vapour, dust, smoke,
and so on. These particles scatter light and change its direction. The presence
of scattering shows distant subjects in pictures as having a veil or haze. The
appearance or effect of this scattering is proportional to the distance of the
objects from the viewpoint. The greater the distance, the greater the amount of
veiling or haze. The effects of this scattering of light are additive, but vary
with atmospheric conditions.
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