camera: Controlling the Light Entering the Camera
Controlling the Light Entering the Camera
The speed of a lens is indicated by reference to its maximum opening, or aperture, through which light enters the camera. This aperture, or
A shutter controls the time during which light is permitted to enter the camera. There are two basic types of mechanical shutter, leaf-type and focal-plane. The leaf-type shutter employs a ring of overlapping metal blades similar to those of the iris diaphragm, which may be closed or opened to the desired degree. It is normally located between the lens elements but occasionally is placed behind or in front of the lens. The focal-plane shutter is located just in front of the film or imaging sensor and has one or two cloth or metal curtains that travel vertically or horizontally across the film frame. Digital cameras may use a mechanical shutter (normally a focal-plane shutter) or an electronic shutter, or a combination of the two; the digital camera in a smartphone uses an electronic shutter. There are two types of electronic shutters. One, known as a global shutter, transfers the data being recorded by the imaging sensor all at once; the other, a rolling shutter, transfers the data line by line. By adjusting the shutter speed in conjunction with the width of aperture, the proper amount of light (determined by using a light meter and influenced by the relative sensitivity of the film or imaging sensor being used) for a good exposure can be obtained.
Sections in this article:
- Introduction
- Development of the Camera
- Motion Picture Cameras
- Features of Cameras
- Controlling the Light Entering the Camera
- Focusing and Composing the Scene
- Bibliography
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.
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