2009

Real-world camera measurements.
A: Focal length
B: Field of view (FOV)
Focal Length
The distance between the lens and the light-sensitive surface, whether film
or video electronics, is called the focal length of the lens. Focal 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.
Focal length is always measured in millimeters. 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.
Field of View (FOV)
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
5208 | Chapter 18 Lights and Cameras