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CCD

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A charge-coupled device or image sensor. It consists of an integrated circuit with an array of linked ("coupled") capacitors which are sensitive to light. In digital photography, the CCD is used to capture images, which in analogue photography would be captured on film. CCD technology is not only used in digital photography, but also in astronomy and other branches of science.

Related Terms

The total number of pixels on a CCD array. This is not always the best indication of a camera's resolution as some CCD chips have a number of pixels around the that are only used to ensure the pixels that are used produce accurate colours. The true indication of a camera's resolution is the two figures quoted, say 1600x1200, which indicate the CCD's actual output. "A ... MP camera" is used to describe a model that has a CCD with a certain number times million pixels, which says something about how big the images are that it can create.
A single, light-sensitive area on a CCD that records unique image detail. This is also referred to as a photosite.
An alternative capture device to the CCD. Its currently as stable as a CCD but has the advantages of higher pixel count, less battery consumption and lower cost.
The CCD used in flatbed scanners and high end cameras which has an array of several thousand RGB filtered elements arranged in a narrow row. The CCD covers the full width of the image and travels down the length of it, scanning one line at a time.
The camera's light sensitive CCD converts the scene into a grid of pixels that make up a digital photograph. The resolution is the total number of pixels in the photo, for example, one million or 350,000. This is one factor that affects image quality, providing the image that's being formed on the CCD is sharp. CCDs with greater numbers of pixels should have higher resolution. Buying adviceUnless you have a specific need for a low resolution model choose a camera with the highest resolution you can afford. This will enable you to make bigger enlargements.
An electronic flash has a maximum distance that it is capable of illuminating. There's also usually a close point where it will start to become too bright and overexpose the subject. The distance from the closest to the furthest point that it can illuminate is the flash range. The range can be increased by using a faster film or more sensitive CCD, and reduced by diffusing the light source using ND filters or material. The range quoted is usually based on using ISO 100 film or a CCD with equivalent sensitivity. APS cameras are, for some reason, quoted using ISO 200 film.
Cameras have various methods of blocking the light from reaching the film or CCD. When a picture is taken this barrier, known as a shutter, will open and allow light to reach the film or CCD. Most cameras have a way of controlling how long the shutter stays open and this duration is known as the shutter speed. More sophisticated cameras can adjust from several seconds to speeds as rapid as 1/10,000sec. Cameras with wider ranges are usually more versatile.Buying advice: Look for a camera that has speeds way below 1/30sec. The longer the speed the lower the light you will be able to take pictures in without having to use flash. As an indication, a speed of around one sec is required to take street lit scenes and a speed of over 30 seconds for moonlit shots. Buy a model with a B setting if you're considering taking extremely long exposures.
A hole in the lens that adjusts in diameter, similar to the way the pupil of an eye works. This controls the amount of light reaching the film or CCD to record an image. Every different diameter opening has a number which indicates the size - it equals the focal length of the lens divided by the diameter of the aperture. These numbers are also called stops. See f/number.
Irregular flaws in image colour or sharpness caused by CCD problems, noise or compression.
Streaks or halos appearing around bright areas of an image that are caused by gross overexposure to the CCD. It's like an electronic equivalent of flare.
A grid of electronic light sensors that convert an image into a digital picture.
A problem with a CCD that makes random colour pixels appear around edges.
Stray electrical charge that appears in areas of the CCD elements that are not exposed to light. The result is irregular noise in image areas such as shadows.
The space between the centres of two adjacent CCD elements.
The amount of light reaching light sensitive material such as film, printing paper or a CCD. Exposure is controlled by the shutter speed (time) and aperture (intensity).
Used to indicate the light sensitivity of a film as ISO. Digital cameras also use the ISO rating to indicate the CCD sensitivity.
Indicates the magnification and angle-of-view of a lens. The human eye sees things roughly the same as a 43mm focal length of a lens for a 35mm camera. Anything shorter is classed as a wide-angle, while longer focal lengths are telephoto. Because of the comparatively small size of the CCD in a compact digital camera it has a standard focal length of between 6mm and 8mm while a medium-format camera is around 80mm.
The area behind the lens where light is gathered to form a sharply-focused image. It's here where the film or CCD is placed.
Used to indicate the light sensitivity of a film. Digital cameras also use the ISO rating to indicate the CCD sensitivity. The standard rating is ISO100 and as this is increased it means that faster shutter speeds can be used. When the ISO is doubled, it doubles the available shutter speed. The drawback for digital cameras is that increasing the ISO increases the amount of digital noise in an image.
The grid of sensors on a CCD that is used to capture an image in a digital camera.
Used to describe a digital camera that has a CCD that delivers more than one million pixels.
A colourless grey filter that's used to evenly reduce the light reaching the film or CCD without affecting the colour.
Another name given to the single, light-sensitive area on a CCD that records unique image detail.
Random coloured pixels that appear in dark or shadow areas when the light levels are below the camera's CCD sensitivity range. Noise is also often seen from scans made using a scanner that doesn't have a wide enough dynamic range to cope with the shadow and highlight areas in one scan. Some image editing programs have a Noise filter that adds a grain pattern to the image to make it look more like a natural photograph taken using film.
Cameras offer different levels of image quality which is determined by lens quality and the resolution (number of pixels) delivered by the CCD. Basic cameras have VGA resolution CCDs that record images with 640x480 pixels. Next up are SVGA models that record 800x600 pixels and then the XVGA models that create pictures with over 1024x768 pixels. The latest super megapixel models go way beyond these figures – currently creating images up to 3040x2016. If you're buying the camera to take pictures for use on screen you only need to buy a VGA model, but if you demand photo quality you need at least a megapixel variety and even then the quality is only good to about 5x7inch from a normal inkjet printer.