Some Commonly Used Lighting Terms and Definitions
What is brightness?
Brightness is the amount of light produced by a surface that reflects or emits more light. It is a subjective term and is not used to describe lighting on a technical level as can’t be measured objectively.
What is illuminance?
Illuminance is the amount of light (luminous flux) falling on a unit area of a surface.
The unit of illuminance is LUX.
What is luminance?
Luminance refers to the amount of light which passes through, emits from, or reflects off an object.
For example the light emitted from a floodlight over a sports field is referred to as luminance while the light falling on the soccer ball on the grass is referred to as illuminance and is measured in LUX.
What is a lamp?
A lamp is commonly referred to as a light bulb meaning the bulb which houses the light source. Lamps are classified into three main types - incandescent, fluorescent, and LED.
Common bulbs or lamps used in outdoor flood lighting and sports lighting include High Pressure Sodium, halogen, and LED.
What is camera illuminance?
Camera illuminance is the quantity of light that shines in the direction of a fixed camera position. This needs to be a consideration for sports lighting systems in venues in which broadcast games are played.
Calculations should be carried out using the actual angles perpendicular to the camera positions. The side of a player forms the reference for a television camera.
The camera illuminance should ideally also be considered for the ball in flight, as this reading will differ from the camera illuminance at ground level.
What is contrast?
Contrast is the differences in appearance between two parts of a visual field seen simultaneously or successively. The difference may be in brightness or colour or both. It is important to pay attention to contrast to ensure all areas of the venue are evenly illuminated.
What is glare?
Glare is the discomfort or impairment of vision experienced when parts of the visual field, such as flood light, are excessively bright in relation to the general surroundings.
Glare can create issues for both players and spectators.
What is a luminaire?
A luminaire is the apparatus which distributes the light emitted by a lamp (a bulb) and which includes all the components necessary for fixing and protecting the lamp and for connecting it to a power supply. It usually consists of a lamp, housing, reflector, lens and control gear.
What is luminous efficacy?
A measure of how efficiently a light source converts electrical energy to light. It is determined by the ratio of light output emitted by a lamp and the electric energy consumed by it.
What is LUX?
The unit of illuminance is the Lux. The lux (symbol: lx) is the SI unit of illuminance and luminous emittance.
Lux is a measure of illuminance, the total amount of light that falls on a surface.
What is rated life in reference to bulbs?
The rated life is the expected average operating life of a lamp (bulb) based on a laboratory test. Usually the longer the rated life the lower the maintenance needs for the lighting system.
What is the stroboscopic effect?
The stroboscopic effect is a flickering effect produced when a rapidly moving object or player passes through an illuminated area periodically varying light, producing the illusion that the object is changing speeds rather than flowing smoothly along a path.
This effect is especially noticeable if discharge lamps are operating on alternating current.
What is the uniformity ratio?
The uniformity ratio is a measure of the evenness of light distribution provided by a lighting installation. The ratio of the minimum lighting level to the average level over a given area.
What is vertical illuminance?
Vertical Illuminance is the quantity of light on a vertical plane and should be calculated during lighting system design to ensure unrestricted camera positions.