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C

Calibration - The act of adjusting the colour of one device relative to another, such as a monitor to a printer, or a scanner to a film recorder. Or, it may be the process of adjusting the colour of one device to some established standard.

Card Reader - A device that you insert flash memory cards into to transfer the data to the computer. Much faster than the serial port! See also "PCMCIA" and "PC Card"

CCD - Charged Coupled Device, a light sensitive chip used for image gathering. In their normal condition these are grey scale devices. To create colour a colour pattern is laid down on the sensor pixels, using a RGBG colour mask (Red, Green, Blue, and Green) The extra Green is used to create contrast in the image. The CCD Pixels gather the colour from the light and pass it to the shift register for storage. CCDs are analog sensors, the digitizing happens when the electrons are passed through the A to D converter. The A to D converter converts the analog signal to a digital file or signal. See also "CMOS" below

CD - CompactDisc - read only storage media capable of holding 650MB of digital data.

CDR - CompactDisc Recordable - a CD that you can write to once that can not be erased but can be read many times, holds 650~700MB of digital data.

CDRW - CompactDisc ReWriteable - the newest kind of CD-R that can be erased and re-used many times, holds about 450MB of data.

Center-Weighted - A term used to describe an auto exposure system that uses the center portion of the image to adjust the overall exposure value. See also "Spot Metering" and "Matrix metering"

CF - see CompactFlash

Channel - One piece of information stored with an image. True colour images, for instance, have three channels-red, green and blue.

Chroma - The colour of an image element (pixel). Chroma is made up of saturation + hue values, but separate from the luminance value.

Chromatic Aberration - Also known as the "purple fringe effect." It is common in two Megapixel and higher resolution digital cameras (especially those with long telephoto zoom lenses) when a dark area is surrounded by a highlight. Along the edge between dark and light you will see a line or two of purple or violet coloured pixels that shouldn't be there.

CIFF - Camera Image File Format, an agreed method of digicam image storage used by many camera makers.

CMOS - Complementary Metal Oxide Semiconductor - Another imaging system used by digicams. It is not as popular as CCD but the future promises us even better digicams based on CMOS sensors due to the lower amount of power consumption versus the typical CCD device.

CMS - Colour Management System. A software program (or a software and hardware combination) designed to ensure colour matching and calibration between video or computer monitors and any form of hard copy output.

CMYK - Cyan, Magenta, Yellow, blacK; These are the printer colours used to create colour prints. Most colour printers, Ink-Jet, Laser, Dye-Sublimation and Thermal printers use these as their printer colours. (This is one of the colour management problems for computers. Converting RGB files to CMYK files cause's colour shifts.) When used by a printer the CMYK is also known as a reflective colour since it is printed on paper, or reflective films.

Codec - Compresses information so that it can be sent across a network faster, and decompresses information received via the network.

Colour Balance - The accuracy with which the colours captured in the image match the original scene.

Colour Cast - An unwanted tint of one colour in an image caused by a disproportionate amount of cyan, magenta, and yellow. This can occur due to an input or output device.

Colour Copier - Colour printing device using electrostatic and CMYK Pigments.

Colour Correction - The process of correcting or enhancing the colour of an image.

Colour Depth - Digital images can approximate colour realism, but how they do so is referred to as colour depth, pixel-depth, or bit depth. Modern computer displays use 24-bit True Colour. It's called this because it displays 16 million colours, about the same number as the human eye can discern.

Colour Space - Digital cameras use known colour profiles to generate their images. The most common is sRGB or AdobeRGB and this information along with the camera and exposure data is stored in Exif header of the JPEG file. This colour space information ensures that graphic programs and printers have a reference to the colour profile the camera used at the time of exposure. see ICC Profile for more information.

CompactFlash - The most common type of digicam flash memory storage. It is removable, small and available in sizes from 4MB up to 1GB.

CF Type I the original 5mm high card

CF Type II cards and devices that are 9mm high. Type I devices are all solid state but Type II devices include the new IBM Microdrive, a miniature, rotating hard drive.

COM port - Your computer has serial communication ports which support the RS-232 standard of communication. This is the most common interface used to transfer data from a digicam to the computer.
Compression - A digital photograph creates an image file that is huge, a low-resolution 640x480 image has 307,200 pixels. If each pixel uses 24 bits (3 bytes) for true colour, a single image takes up about a megabyte of storage space. To make image files smaller almost every digital camera uses some form of compression. See the "JPG" entry below.

Continuous Autofocus - (Continuous-AF) The autofocus system is full-time and works even before the shutter release is pressed.

Continuous Tone - An image where brightness appears consistent and uninterrupted. Each pixel in a continuous tone image file uses at least one byte each for its red, green, and blue values. This permits 256 density levels per colour or more than 16 million mixture colours.

Contrast - A measure of rate of change of brightness in an image.

CRW - The raw CCD file format used by Canon digicams. Abbreviated from CanonRaW.

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