How Digital Cameras Work
Basics
Digital cameras operate on the same basic principles as film cameras. Both have an optical lens that gathers light and focuses it onto a recording surface. Similarly, both have a shutter that opens in adjustable intervals to control the amount of exposure and an aperture (or opening) that controls how much light the camera is exposed to.
The chief difference between a digital and film camera is the medium used for capturing the exposed image. A film camera uses photographic film, composed of special plastics and a light-sensitive chemical called silver halide. The image makes an impression on the film, which is then developed through a chemical process and printed into photographs.
Image Sensor Chip
A digital camera, on the other hand, contains an image sensor chip instead of photographic film. While several types of image sensors are used in digital cameras, they all operate in roughly the same way. Basically, an image sensor chip works by converting the optical information contained in an image into electrical information, such as a computer file.
Image sensor chips are composed of individual units called photo sensors, which accumulate an electrical charge when struck by photons from light. This electrical charge is then converted by the circuitry in a camera into a digital image composed of pixels. After a digital image has been created, it is stored in the camera's memory chip.
Advantages
The image sensor gives digital cameras several advantages over traditional film cameras. As no complicated development process is involved, the picture can be viewed immediately after the camera has finished processing it. The storage capacity of a memory chip also allows some digital cameras to double for a video recorder by constantly taking pictures. Because a digital camera generates digital images, no scanner is required to upload your photographs to your computer. Finally, digital cameras are entirely electronic and can be made much smaller than a film camera, allowing them to be built into devices such as cell phones and PDAs.
Pixels
A digital image, such as the one a digital camera produces, is composed of tiny units called pixels. Each pixel substitutes for a tiny piece of the original image by replicating its brightness and color. Thus, the more pixels a digital image contains, the more accurately it represents the original image. For instance, if not enough pixels are present to accurately represent an object in a photograph, it may appear fuzzy or blurry. On the other hand, the more pixels an image contains, the more crisp and clear it appears.
Megapixels and Photo Quality
In the case of digital cameras, pixels are discussed in terms of megapixels (MP), which means one million pixels. When you purchase a digital camera that produces seven megapixel photographs, for example, your pictures will be composed of seven million individual pixels. How many megapixels a camera is capable of producing is a product of how good its image sensor chip is. That's why cameras capable of taking pictures with more megapixels are usually more expensive than their counterparts.
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