Basic Lighting Terminologies

The emission or transfer of energy as electromagnetic waves.

Electromagnetic radiation that humans can see.

Range of wavelengths that produce a visual sensation.

Eye cells for black/white vision at low light levels.

Eye cells for color vision at higher light levels.

Amount of light emitted by a lamp.

Light output per unit of electrical power.

Amount of light on a surface.

Light intensity reflected from a surface.

The human eye's sensitivity to different wavelengths of light (colors).

The unit of measurement for illuminance, representing the amount of light falling on a surface.

How well a light source represents the true colors of objects compared to a reference light source (like daylight).

A numerical value that measures how accurately a light source renders colors compared to a reference source (daylight).

A measurement of the color of light emitted by a light source, expressed in Kelvin (K).

A theoretical object that absorbs all radiation and emits light at a specific color based on its temperature

Uncomfortable or distracting brightness or light intensity that reduces visibility.

The ratio of the total light output from a luminaire (lamp fixture) to the combined output of the individual lamps within it.

Measures the proportion of light emitted downwards by a luminaire compared to the total light output.

The ratio of the light reaching the work area to the total light output from a luminaire.

The three categories are: 1) 5300K: Cool (bluish white) 2) 3300-5300K: Intermediate (white) 3) 3300K: Warm (reddish white)

The ratio of the lumens produced by a lighting system while in service to the lumens produced when it was newly installed. It accounts for light output decrease over time due to factors like dirt accumulation and lamp aging.

A dimensionless metric that represents the size and shape of a room relative to the luminaires. It influences the light distribution and uniformity.

The ratio of the minimum illuminance on a surface to the average illuminance. It indicates how evenly light is distributed.

The gradual decrease in light output of lamps over time, which varies depending on lamp type and manufacturer.

A higher C.O.U. means more of the light from the luminaires reaches the work plane, resulting in better lighting efficiency and less energy wasted.

A larger room index indicates a larger room relative to the luminaires, resulting in more light being lost due to reflections and absorption by the walls and ceiling, leading to lower illuminance levels.

It helps account for real-world lighting conditions, where light output decreases over time due to factors like dirt and lamp aging. It ensures accurate lighting calculations for long-term use.

A high uniformity ratio indicates a more evenly distributed light, creating a more comfortable and visually pleasing space by eliminating areas of glare or excessive brightness.

LLD ensures accurate illuminance calculations over time by accounting for the gradual light output decrease of lamps. It helps avoid overestimating the light output of a system, ensuring adequate illumination throughout the system's lifespan.

Rods and cones are the two types of photoreceptor cells found in the retina of the eye. They are responsible for different aspects of vision.

Scotopic vision, enabled by rods, refers to black and white vision at low light intensity. Photopic vision, enabled by cones, refers to color vision at higher light intensity.

Luminous flux is the total amount of light emitted by a light source, measured in lumens.

Illuminance is the amount of light falling on a surface, measured in lux.

Luminance is the intensity of light reflected from a surface, measured in candela per square meter.

Color temperature refers to the color of light emitted by a light source, measured in Kelvin (K).

The Color Rendering Index (Ra) measures how accurately a light source reproduces the colors of objects compared to daylight, ranging from 0 to 100.

Glare is uncomfortable or distracting brightness that reduces visibility, often caused by poorly directed or excessive light.

The Coefficient of Utilization (C.O.U.) represents the ratio of light reaching the work area to the total light output from a luminaire (lamp fixture).

1. 5300°K: Cool (bluish white) 2) 3300 - 5300°K : Intermediate (white) 3) 3300°K : Warm (reddish white)

A larger room index indicates a larger room relative to the luminaires, resulting in more light being lost due to reflections and absorption, leading to lower illuminance levels.

A high uniformity ratio indicates a more evenly distributed light, creating a more comfortable and visually pleasing space by eliminating areas of glare or excessive brightness.

The Coefficient of Utilization (C.O.U.) depends on factors like: The light distribution of the luminaire, the light output ratio of the luminaire, the reflectance of the ceiling, walls & working plane, the room index, and the arrangement of the luminaires in the room.

Electromagnetic radiation that humans can see, spanning wavelengths between 380 and 760 nanometers.

Black and white vision enabled by rods in the eye, active at low light intensities.

Color vision enabled by cones in the eye, active at higher light intensities.

C.O.U. (Coefficient of Utilization) is influenced by factors like:

1. How the luminaire distributes light
2. The luminaire's light output ratio
3. The reflectivity of surfaces like the ceiling, walls, and the workplane
4. The room index
5. Arrangement of luminaires in the room

C.O.U. indicates how efficiently light from a luminaire reaches the work area. It helps ensure that the right amount of light is available where needed.

A higher C.O.U. means more light reaches the workplane, leading to better lighting efficiency and less energy wasted.

It helps ensure accurate lighting calculations over time, taking into account the gradual decrease in a lamp's light output. This prevents overestimating the light output for the entire lifespan of the lighting system.