An A-to-almost-Z for those who can't tell a pixel from an f-stop. Impress the sales folk with your fluency in camera talk Aperture: The size of the opening of a lens, often referred to as an 'f-stop', as in f/11 or f/8. The larger the f-number, the smaller the aperture and amount of light entering the camera lens. You can find the actual aperture by dividing the focal length of the camera by the f-number. A 110mm camera with an f-stop of 5.6 gives an aperture of about 19.6mm. Buffer: Memory that the camera has to store digital images before they are written to the memory card. This is important if you are looking to snap a series of action images. CCD: A charge coupled device is one of the two main types of image sensors used in digital cameras. In a CCD, every pixel's charge is transferred through a limited number of output nodes to be converted to voltage, buffered and sent off-chip as an analogue signal. CCDs are often used where image quality is crucial. CMOS: A complementary metal-oxide semiconductor is the second of the two main types of image sensors used in digital cameras. In a CMOS imager, each pixel has its own charge-to-voltage conversion, and the sensor often includes digitisation circuits, so that the chip outputs digital bits. These other functions reduce the area available for light capture, and with each pixel doing its own conversion, uniformity drops. However, the chip requires less off-chip circuitry for basic operation. CMOS imagers are used where space is limited and image quality is not paramount. EXIF: Exchangeable image file format is used in most digital cameras. When a typical camera is set to record a jpeg, it is actually recording an EXIF file that uses jpeg compression to compress the photo data within the file. F-number (or F-stop): The ratio of the focal length of a lens or lens system to the effective diameter of its aperture. Fill flash: A flash technique used to brighten dark shadow areas formed, especially on sunny days. Some digital cameras feature a 'fill flash' mode that forces the flash to fire even in bright light. ISO speed: This represents the film's sensitivity to light. Although digital cameras do not use film, they adopt the same rating system for describing the sensitivity of the camera's imaging sensor. Most digital cameras include a control for adjusting the ISO speed. (Generally, in dimmer lights, the ISO speed climbs but the image quality drops.) Jpeg: A standard for compressing image data developed by the Joint Photographic Experts Group (hence the name). Despite its daily usage in describing a type of image file, jpeg is not a file format. It is a compression method that is used within a file format, such as the EXIF jpeg format common to digital cameras. Usually, if a high-quality, low-compression jpeg setting is chosen on a digital camera, the loss of quality is not detectable to the eye. Pixel: Picture Element is the building block of a digital photo. RAW: The RAW image format is the data as it comes directly off the CCD, when no in-camera processing is performed. Some photographers like using RAW images, while others prefer the time savings afforded by jpeg files. It makes sense to shoot in RAW if you are uncertain about what colour temperature is optimal (especially with sunrise/sunset shots). Once a digital camera has assigned the white balance (WB) setting to a jpeg file, there is not much of a chance to alter the shot later. With RAW files, photographers can wait till they get to their PC monitors before deciding which WB setting is best. Red eye: A red glow is emitted when a flash reflects off the blood vessels behind the retina of the subject's eyes. When captured on an image, it looks as if the subject's eyes have been replaced by red bulbs. The effect is most common when the light level is low, and when shooting outdoors at night or indoors in a dimly lit room. White balance (WB): A camera function that compensates for different colours of light being emitted by different light sources. White balance can be used to influence a photograph's 'mood'. Before digital, photographers depended on glass filters to 'colour correct' a scene, or they used specialised film to match the environment. As with many things, things go better with digital.