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The Basics of Digital Photography

 

            
             Digital cameras are rapidly replacing traditional analog and film cameras. Despite their notable success in the market, most digital cameras today still fall behind film cameras in image quality and great efforts are being made to improve their performance. Since digital cameras are complex systems combining optics, device physics, circuits, image processing, and imaging science, it is difficult to evaluate and compare their performance logically. .
             Derived by the demands of multimedia applications, digital still and video cameras are rapidly becoming well-known. As image acquisition devices, digital cameras are not only replacing traditional film and analog cameras for image captures, they are also enabling many new applications such as PC cameras, digital cameras integrated into cell phones, toys, biometrics, and camera networks.
             2. Working Principle of the Digital Camera .
             In the block diagram shown in Figure 1, a typical digital camera system. In this figure, a scene is focused by a lens through a color filter array onto an image sensor which converts light into electronic signals. The electronic output then goes through analog signal processing such as correlated double sampling (CDS), automatic gain control (AGC), analog-to-digital conversion (ADC), and a significant amount of digital processing for color, image enhancement and compression. The image sensor plays a pivotal role in the final image quality. .
             3. Current Features of the Product .
             3.1 Sensors.
             Digital cameras today use charge-coupled device (CCD) image sensors. In these types of devices, the electric charge collected by the photo detector array during exposure time is serially shifted out of the sensor chip, thus resulting in slow readout speed and high power consumption. CCDs are fabricated using a specialized process with optimized photo detectors. To their advantages, CCDs have very low noise and good uniformity. It is not feasible, however, to use the CCD process to integrate other camera functions, such as clock drivers, time logic and signal processing.


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