Technical

On Lighting Design

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A space deprived of light does not have a soul. Light bridges the gap between space and time. Emotionally, light warms in the cold and cools in the warm. Lighting design is the art and science of refining light to achieve visual comfort and functionality.

Outlines

  1. Our Visual Field
  2. Units of Measurements
  3. Correlated Colour Temperature
  4. Lighting Control
  5. Mounting Methods of Light Fittings and Their Functions
  6. TM-30 Colour Rendering Evaluation

Our Visual Field

Stack Exchange. “Image of Interest.” Imgur, https://i.stack.imgur.com/9rD4r.jpg.

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Units of Measurement

Luminous intensity (candela, cd)1 refers to the perceived brightness by the human eye. It measures the amount of light radiated in a specific direction from a light source.

Luminance (candela per square meter, cd/m2)2 refers to the human eye’s perceived brightness of an overall surface. It measures the amount of light radiated or reflected by a surface. The measurement considers the colours and textures of the surface.

Illuminance (lux, lx) refers to the amount of light distributed per square meter over a surface area. It is an essential parameter in lighting design that influences the space’s visibility, comfort, and overall functionality.

Converting from candela to lux
Converting from lumen to candela

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Correlated Colour Temperature

Correlated colour temperature, CCT (Kelvin, K) refers to the colour appearance of a light source. It is correlated to the light emitting from a heated black-body radiator. A light source with a higher CCT will appear cooler, while the opposite will appear warmer. It does not capture the full complexity of colour rendering (refer to TM-30).

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Lighting Control

What are the methods of controlling light fittings?

  1. Manual switches and dimmers
    • On/off switch
    • Phase dimmer switch
    • 0/1-10V dimmer switch
  2. Sensors
  3. Timer
  4. Remote controls
  5. DALI (Digital Addressable Lighting Interface)
  6. Smart lighting systems
    • Centralised
      • KNX
      • Lutron
    • Wireless mesh networks
      • Casambi (Bluetooth)
      • Tuya (Bluetooth + Zigbee)
      • Zigbee
    • Voice control
      • Amazon Alexa
      • Apple Siri
      • Google Assistant

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Mounting Methods of Light Fittings and Their Functions

What are the several types of mounting methods and their functions?

  1. Bollard (floor wash)
  2. Inground (up-light, wall wash, marker, or side emitter)
  3. Wall recessed (floor/ceiling wash)
  4. Wall surface-mounted (single/double emission, backlit)
  5. Ceiling recessed (downlight, wall wash)
  6. Ceiling surface-mounted (downlight, wall wash)
  7. Pendant (single/double emission, ambient)

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TM-30 Colour Rendering Evaluation

TM-30 is a method for evaluating the colour rendering of light sources. There are three key parameters:

  1. The fidelity index (Rf)3 represents the accuracy of the colour rendering for CES compared to a reference light source5.
  2. The gamut index (Rg)4 represents the average saturation change CES.
  3. The colour vector graphics represent the colour rendering properties compared to a reference light source.
Colour evaluation samples (CES)6
Colour vector graphics6

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1 – One candela (cd) is one lumen per steradian (lm/sr).
2 – It is also known as a nit.
3 – Possible values range between 0 to 100.
4 – Possible value range between 0 to 150.
5 – Reference light source refers to natural light, Rf 100 and Rg 100.
6 – Courtesy Nichia