Inside a Digital Camera

By Wilfred Ursley

In a nutshell, a digital camera uses a lens or series of lenses to focuses light onto a sensor. This sensor then records the image electronically and transfers it to the electronic workings of the camera where it is organized, converted into binary digital data, and then stored on fixed or removable memory to be later read by a computer. Of course this is a highly simplified explanation of how a digital camera works.

Most digital cameras’ sensors are charge-coupled devices, or CCDs, although some cameras instead have a complementary metal oxide semiconductor, or CMOS. Either way, light is converted into electrical charges, which are transferred to the brain, and finally onto the storage media.

As part of this process the sensors filter the light into the three primary colors, which can be combined to create the full spectrum. The more expensive (and higher quality) cameras use three separate sensors to accomplish this task. Each sensor is fitted with a filter of a different color, making it read only the light that matches that color.

The amount of light reaching the sensor is also controlled carefully. Cameras do this in two ways: aperture size, and shutter speed. Most of today’s cameras have automated aperture settings, although some models allow manual control, which enthusiasts and professionals prefer. Shutter speed is generally set electronically.

There are four kinds of lenses used by digital cameras: optical-zoom lenses with automatic focus; fixed-focus, fixed-zoom lenses; digital-zoom lenses; and replaceable lens systems. Optical zoom lenses have both telephoto and wide options, while the fixed focus and fixed zoom lenses are used in the ordinary, inexpensive cameras that infrequent users own. The digital zoom lens creates the illusion of a zoom effect by culling pixels from the central part of the image and enlarging them to fill the frame. This, however, often results in a grainy or fuzzy image at the extreme limits of the camera’s capabilities.

An LCD screen is standard on most digital cameras today, and they help in previewing images and also checking them out after taking a shot. Many screens are rather small, because there is only so much space on a camera for them. It is always best to transfer the images to a computer for viewing. In terms of image quality in general, the higher resolution the camera, the better the image quality.

For printing photos, resolution of the original image is also key. A low quality camera such as those found in many cell phones will create images that are really only useful for emailing or for web pages. A 2-megapixel camera produces images that can be blown up to about 4×6 inches. Four megapixels will create nice 16×20 inch images, but with falling prices on most digital cameras, if you enjoy photography and enlarging photos, don’t settle for less than six megapixels.

Several years ago, digital cameras stored images onto fixed memory locations inside the camera. Users needed a cable to hook up to a computer in order to transfer images. Today’s cameras all use removable, reusable memory media, and are therefore much more flexible and convenient. Larger amounts of storage are easy to purchase, so one can also take higher resolution pictures without fear of running out of memory. Various systems for storage include SmartMedia cards, memory sticks, and CompactFlash cards. Other cameras use microdrives, like little hard drives, or DVDs. Whichever method your camera uses, the convenience and freedom that digital photography allows will turn you into a shutterbug in short order!

Author Wilfred Ursley is a writer for several popular web magazines, with tips and resources on consumer electronics and alternative health subjects.

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