Glossary » C

A unit of luminous intensity per projected area of a light source, from a given direction. Based on the light generated from a single candle flame, which is equivalent to one candela.

Also known as digitising. The process of recording video from one source to another such as a camcorder to a PC hard drive.

Column Address Strobe - one of several memory latency settings in the BIOS. Latency is the memory timing, or the time it takes for the memory to be refreshed, this is measured in milliseconds. The CAS value is predefined in the SPD chip on the memory module and most modern motherboards defaults to the SPD settings. On more expensive memory this value has been tweaked to offer lower latency.

Charge Coupled Device. A type of silicon chip used in many imaging devices. Employs a grid of light sensitive elements which store electrical charge proportional to amount of light falling on them. Charge later converted into digital information for further processing.

Intel’s budget range of CPUs, available in several different configurations depending on what interface the current range of performance CPUs are using.

Also known as Colour Key or Blue Screen. Technique that replaces areas of video with a particular colour with another image.

The colour element of a video signal (hue and saturation).

Complementary Metal Oxide Semiconductor. Alternative imaging technology traditionally used in budget webcams, but now employed in many high-end cameras like Canon’s digital SLRs.

Communications Network Riser - a connector for certain add-on cards and most commonly used for modem upgrades. The advantage of CNR is that the slot has a direct bus to the southbridge of the motherboard and thus avoids some of the congestion that is common over the PCI bus. There are also CNR sound upgrades available for some motherboards with integrated sound.

COder/DECoder. Used to describe any method of compressing video such as MPEG2, Indeo, DivX, Windows Media, Real Media.

A monitor’s ability to maintain the same colours when the intensity of the screen is varied. It can also be used to describe the correct combination of colours that make up a scanned or printed image or photo. An image that has a good colour balance will contain neutral greys, have no underlying colour cast, and will match the original closely.

Colour depth refers to the number of colours that can be manipulated, calculated or displayed on screen at any one time by any given hardware or software. The number of available colours is dependent on the number of bits of colour data used for each pixel, which is why colour depth is sometimes referred to as bit depth. As a guide 4 bits = 16 colours, 8 bits = 256 colours, 16 bits = 64 thousand colours, also called high colour, and 24 bits = 16 million colours called true colour.

A property of a colour display describing the uniformity of a specific colour across the surface of the display. If purity is poor, a plain white image may be slightly redder or greener in the areas affected. This can be a product of an uneven phosphor coating.

A measurement of the colour of light radiated by the Black Body Radiator (a theoretical body that is completely non-reflective, that has no melting or boiling point). A light source’s colour temperature is the temperature (in Kelvin) at which the Black Body Radiator has to be heated to in order to radiate light that matches the said source. For example, 9300K is bluish, 2400K is reddish, and white or neutral temperature is around 6500K.

A high quality video standard used on high-end AV equipment such as DVD players and projectors. Component video separates the video signal into three parts, luminance (light), blue chrominance (blue colour) and red chrominance (red colour). These three parts are often referred to as Y, Pb and Pr. The three parts of the video signal are transported discretely along the separate cables to ensure the highest possible quality. There is no need to transport a green signal since anything that isn’t blue or red is assumed to be green.

This is the most simple method of video transporting often through an RCA connector. It also offers the worst video quality.

The process of combining multiple visual elements or layers into a single image.

Mathematical formulas used to identify redundant information in a digital file and remove it to save storage space or transmission time. Compression can either operate in a lossless form where there is no loss of quality, or lossy which reduces quality, but can significantly decrease file sizes.

The level of variation between light and dark areas in an image.

The ratio of intensity between the brightest white and the darkest black of a display’s picture. For example, 500:1.

Describes how well the CRTs’ electron beams from the red, green, and blue electron guns intersect at each pixel. The better the convergence, the sharper the image will look.

Central Processing Unit, this is the brain of a computer and is often referred to as the processor. This is usually one of the most expensive parts of a computer even though it is one of the smallest. The CPU does all data processing and calculations. CPU manufacturing is a very complicated process and consequently it’s very expensive too. That’s why the latest CPUs command quite a hefty price tag.

Shimmering or flickering effect seen in fine detail monochrome scenes. Commonly found in composite video connections.

Cathode Ray Tube. Briefly, the technology behind a CRT is based on the use of electron guns, mounted at the rear of a partially evacuated glass tube. These guns consist of a heated cathode that liberates electrons, which are then focused by electromagnets in order to produce an intensity-controlled fine beam of negatively charged electrons. These are then attracted by a positively charged high voltage anode and steered by electromagnets so that the beams are scanned in a raster across the inner face of the tube. Here the beams are ‘filtered’ by either a shadow mask or an aperture grille so that they hit and excite red, green and blue phosphor elements coated on this inner surface, ultimately producing the desired picture on the screen.

This is a texture map used to define what can be seen in reflective surfaces. It defines a texture for the four planes of a cube, front, back, left, right, up and down.