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glossary of terms > glossary of terms - Pg. 191

Resolution Measure of the amount of information in an image expressed in terms of the number of pixels per unit length (i.e. pixels per inch). Camera resolution is usually defined as the actual number of pixels in an image i.e. 640 x 480 (see also DPI and PPI). Reticulation An irregular clumping of silver on the emulsion, usually happens when the film has been exposed to sudden or severe temperature changes. Reversal film A photographic film that produces a transparent positive image, or a slide. RGB Red, green and blue. TV sets, monitors and digital cameras use a mix of RGB to represent all the colours in an image. Ring flash A circular, electronic flash unit that is placed around the lens. Produces a flat light, with a fine halo effect around the subject. Serial transfer Connecting a digital camera to a computer via the serial ports in order to download images. Shutter The curtain-like camera mechanism that, when set and activated, determines the duration of exposure, or light falling onto the film. Works in conjunction with the aperture. Shutter lag The delay between pressing the fire button and the camera actually taking a picture. Most notable on compact digital cameras, where the camera has to switch from providing a picture to the LCD, meter the scene using any preset options, reset the CCD and open the shutter. Earlier, and currently cheap, models were very poor in this regard. Shutter speed The time for which the CCD or film is exposed during an exposure. High shutter speeds (hundredths or thousandths of a second) prevent camera shake and can freeze motion in photos. Softbox A lightweight frame with a soft, white diffusing material stretched across it. Placed over the head of a light (usually studio flash), it gives a soft, even light on the subject. Spot metering A two degree spot circle in the centre of the viewfinder where the metering system reads the light, ignoring all other elements in the picture. The value from the spot is used for the exposure. Stop The f/number for an aperture setting. On a camera or an enlarger lens in the darkroom a photographer will `stop down' to reduce the aperture. Stop bath Chemical used to neutralise the developer and completely stop the development stage. Super zoom A general term for a zoom lens with a very big range of focal lengths. A 28-300mm zoom would be an example. USM Unsharp Mask. A tool in many software image editing packages, and a vital one in digital imaging. It makes photos appear sharper by giving more contrast to the boundaries between colour areas. UV filter A colourless filter used over the lens to absorb ultra-violet rays and, to some extent, general haze. Many users fit screw-in UV filters to expensive lenses to prevent any chance of scratches or damage. Viewfinder The scene, or view or subject range, seen from the camera. Wetting agent A detergent type chemical, greatly diluted to reduce surface tension of water on film. Used in the final stage of development prior to drying to help prevent drying marks. Wide-angle lens A lens with a short focal length but a wider angle of view than a standard lens.