Bright spots of light, normally taking the form of the lens diaphragm, which appear in a camera viewfinder or in a recorded image when a lens is directed close to an intense source of light. Multi-layer coating of filters and lens elements helps reduce the effect, but cannot completely eliminate it. The effect is not always undesirable.
One thousand million (one billion) bytes of computer data - equivalent to 1,000 Megabytes.
A cardboard or metal shape used with a suitable light source to project a controlled shadow onto a subject. Gobo are normally used inside a focusing spot lights.
A filter whose density of colour changes smoothly either from maximum to minimum or from one colour to another.
The appearance of a single light-sensitive crystal or individual dye cloud in a processed image.
If all the tones in a typical image are mixed together, the result would be 18 per cent grey. A standard grey card reflects 18 per cent of the light falling upon it, and is therefore regarded as a standard against which exposures can be measured, and reflected-light exposure meters calibrated.
A set of defined brightness steps used by a system. An 8-bit scanner digitizes to a 256-step scale from 0 (black) to 255 (white).