Communication and Media Technology – Digital Cameras
Traditional film cameras are rapidly being replaced by digital models. Instead of using photographic film, today they are equipped with high-resolution digital sensors.
A basic camera is an opaque-fronted box containing a photodetector on its back. Earlier, the sensor was a strip of light-sensitive photographic film; however, today an electronic chip is used. Light reaches this chip through optical lenses in the camera’s opposite side.
Shutter and aperture
The shutter of a digital camera regulates the sensor’s exposure time. Usually open for just a fraction of a second, it must remain as such until the sensor has received sufficient light to produce an image. A short exposure time allows the photodetector to capture a clear image of a target, even if it is moving rapidly. Longer exposure times blur the movement, a desired effect in art photography. The amount of light reaching the sensor depends on the aperture, or circular opening within the lens.
This device is similar to the iris in the human eye. The shutter speed and aperture setting must be coordinated: if the exposure time is short, the aperture must open wide, and vice versa. The aperture setting also affects the sharpness of the picture. A small opening means increased sharpness, and a greater depth of field. A larger aperture setting reduces the depth of field. More modern cameras can automatically adjust these settings.
The photographic lens
The camera’s lens assembly is focused to form the sharpest possible image on the sensor. It usually consists of several optical lenses, to compensate for color or image distortions. A standard lens captures a scene with al- most no magnification, while a wide-angle lens has a short focal length, allowing the sensor to capture broader views, such as landscapes.
The long focal length of telephoto lenses produces a narrow picture angle making distant objects that appear small fill the photo. With a zoom lens the focal length can be changed, while the focus remains sharp, allowing the user to change the size of the image and adjust the viewing angle.
PHOTO DETECTORS
A digital camera’s sensor contains tiny, light sensitive semiconductor pixels arranged In a checkerboard pat tern. As light enters the camera and falls upon each pixel, it releases a certain number of electrons depending on the light intensity.
The values of the resulting electrical charges are then measured. As every pixel is also covered by a red, green, or blue filter, the light’s color value can also be measured, producing a color photograph.
BASICS
THE NUMBER OF PIXELS used by modern digital cameras is more than sufficient.
Thus, more important factors for picture quality include the size of the sensor and its photo elements, the quality of the lens, and the skill of the photographer.