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Characteristics of Cameras 1217
Using Cameras
Characteristics of Cameras
Real-world cameras use lenses to focus the light
reflected by a scene onto a
focal plane that has a
light-sensitive surface.
Real-world camera measurements.
A: Focal length
B: Field of view (FOV)
Focal L ength
The distance between the lens and the
light-sensitive surface, whether film or video
electronics, is c alled the
focal length of the lens.
Foca l length affects how much of the subject
appears in the picture. Lower focal lengths include
more of the scene in the picture. Higher focal
lengths include less of the scene but show greater
detail of more distant objects.
Focallengthisalwaysmeasuredinmillimeters.A
50mm lens is a common standard for photography.
A lens with a focal length less than 50mm is
called a
short or wide-angle lens. A lens with a
focal length longer than 50mm is called a
long or
telephoto lens.
Fi eld of View ( F O V )
The field of view (FOV) controls how much of the
scene is visible. The FOV is measured in degrees of
the horizon. It is directly related to the focal length
of the lens. For example, a 50mm lens shows 46
degrees of the horizon. The longer the lens, the
narrower the FOV. T he shorter the lens, the wider
the FOV.
Relati onship Between FOV and
Per specti ve
Short f ocal lengths (wide FOV) emphasize the
distortions of perspective, making objects seem
in-depth, looming toward the viewer.
Long focal lengths (narrow FOV) reduce
perspective distortion, ma king objects appear
flattened and parallel to the viewer.
Upper left: Long focal length, narrow FOV
Lower right: Short focal length, wide FOV
The perspective associated with 50 mm lenses
appearsnormal,partlybecauseitisclosetowhat
theeyesees,andpartlybecausesuchlensesareso
w idely used for snapshots, news photos, cinema,
and so on.
Dif ferences B etween Camer a Obj ects
and R eal-World Cameras
Many other controls on real-world cameras (such
as those for focusing a lens, and advancing film)