On Angle of View

 

Some compact cameras mention that, “the focal length, 4.3–180mm has an angle of view equivalent to that of 24–1000mm lens in 35mm format.” Could you please tell me what “angle of view equivalent to that of a 24–1000mm lens” refers to?
Arunangshu Datta, New Delhi, via email

Think about the field of view of your eyes when you are looking in one fixed direction. If you do not include peripheral vision, the field of view is between 45° to 50°. This is considered to be ‘normal’. This is also the angle of view produced by a 50mm lens on a full-frame sensor. (Thus, making the the 50mm lens a ‘normal’ lens.) If you narrow this field of view, you get telephoto view. If you broaden it, you get wide angle FoV. Zoom lenses allow you to diminsh or broaden the the field of view by zooming in or out.

With the popularity of regular 35mm film, it became a standard for comparison of focal lengths. With the coming of digital imaging, sensor sizes became much smaller than regular 35mm film. Thus, the focal length required to create a ‘normal’ field of view also reduced. A 50mm lens has a ‘normal’ field of view for a 35mm sensor, but the same FoV is produced at about 9mm on a compact camera with a 1/2.3-inch sensor. Continually, 4.3mm has the approximate FoV of a 24mm lens and 180mm becomes roughly 1000mm.

Tags: angle of view, ask the expert, focal length, Lenses, May 2015