human eye. Wide-angle lenses have a large or wide
telephotolenses) have a narrow angle of field (fig. 1-21).
lens-to-film distance remaining unchanged. Angle of
view is an angle with the intercept point at the lens and
its sides matching the corners of the film.
exceed the angle of field of the lens. Any lens recording
has a short-focal length and is called a wide-angle lens.
Any lens with an angle of view less than 45 degrees with
a given film size has a longer focal length.
other recording medium). This opening can be made
larger or smaller to allow more or less light to pass
through the lens. When the diaphragm opening is very
sharp focus. As the diaphragm opening is reduced (made
behind the point of focus become sharper. The lens
diaphragm is used in conjunction with the shutter of
the camera to control the amount of light to expose
dimension, depth, is suggested by the relative size and
position of the various objects in a picture. Perspective,
which is the relationship of objects in a photograph,
affects the naturalness of a picture. Good perspective
represents objects as they actually appear to human
part of the story. Lenses of different focal length are also
used to control perspective.
But a choice of lenses of a different focal length does
enable you to get the desired image size at the selected
distance for best perspective. For example, suppose you
come across a placid farm scene. A rustic rail fence is in
the foreground, and a cow is munching on a haystack in
the field. The cow and her lunch are 100 feet behind the
essential to your picture and you use a 50mm lens. The
result! The cow is 110 feet from the camera and is too
small in relation to the fence. Your picture is a flop. Now
change your perspective. Back up 40 feet from the fence
Basic Photography Course