Light quality in depth

COLOUR TEMPERATURE OF LIGHT

The scale ranges from 1,000 K to 16,000 K (K = degrees Kelvin)

The spectrum of light emitted from an INCANDESCENT object (= heated to the point of producing light radiation) changes with increasing temperature, from red to orange, and then to yellow, white and blue.

White LEDs generally have a temperature, and therefore a colour, that ranges between 2,200 K and 6,500 K.

COLOUR RENDERING INDEX (CRI or Ra)

An index, on a scale of 0 to 100, which rates the ability of an LED to faithfully reproduce the colours of illuminated objects with respect to natural light. The smaller the difference, the better the quality of light (and therefore the higher the CRI).

A good CRI is considered to be ≥ 90 (LE+D supplies LED with a CRI of 94–96).

OPTICAL DIFFUSER (OPALESCENT COVER)

As LED lights emit points of light, in order to guarantee uniform diffusion of light in strip fixtures, it is necessary to use an optical diffuser, which can come in different shapes and materials:

  • POLYCARBONATE
  • METHACRYLATE
  • RESIN

Opalescent covers ‘absorb’ some of the light emitted, and therefore reduce its intensity by about 40–50%.
For the best results, the design of strip lighting fixtures must take into account various factors:

  • The distance between the LEDs (and therefore between points of light)
  • The distance between the light source and diffuser
  • The choice of diffuser material and thickness
  • The geometry of the diffuser
OPTICAL LENS

This is an optical element that has the ability to focus and direct light. It is normally made out of glass or plastic.

Types of lenses used by LE+D:

  • Conical, with various degrees of opening
  • Elliptical
  • Linear
TYPES OF CABLE

Cables used by LE+D are manufactured to our specifications so that they conform to all applicable electrical safety standards (CE, LSZH, CPR, UL, etc.)

LED DRIVER

This is a switching electric power adapter which has the task of converting alternating current from the electricity supply to constant direct current, ensuring that an LED lighting appliance meets all performance requirements and standards.

MAGNETIC FIXINGS

The use of magnets as a fixing system is a characteristic of LE+D products.

MAGNETS: Rigid metallic fixings that have been given a magnetic charge. They come in different shapes, types and magnetic strengths, and can be single pieces or continuous magnetic strips.

LUMINOUS FLUX (lumen or lm)

The total amount of light emitted by a light source

LIGHT EFFICIENCY = lm/W

The relationship between luminous flux and the power required to produce it. This value is also an indicator of the energy efficiency of a light fixture

LIGHT INTENSITY (cd)

This is measured in CANDLES = the amount of flow from a point source of light in a specific direction

ILLUMINANCE (Lux or lx)

lm/m2 = the relationship between the luminous flux (measured in lumen) emitted by a light source and the surface of an illuminated object

PHOTOMETRY

The science of MEASUREMENT OF THE PERCEIVED BRIGHTNESS OF LIGHT = OPTICAL magnitude:

  • Luminous flux (lm)
  • Light intensity (cd)
  • Illuminance (lx)
SPECTROPHOTOMETRY

Spectrophotometry deals with the study of the visible light spectrum, from near ultraviolet to near infrared. It requires the use of a spectrophotometer, a device for measuring light intensity, which is determined as a function of the wavelength of light radiation.

Definitions

LED (Light Emitting Diode)

A light-emitting diode is an electronic device that exploits the capacity of certain semiconductor materials to produce photons via spontaneous emission.

LED BOARD

This is an electronic circuit board featuring various types of circuitry to ensure proper function of LEDs. The circuitry is mounted on a printed circuit board (PCB) made of vetronite or aluminium.

The PCB is a device used to connect different electronic components to each other via conductive tracks printed on a non-conductive material; it also ensures that the heat generated by the LEDs is transferred to the heat sink.

HEAT DISSIPATION

LEDs convert roughly 45% of the energy supplied into visible photons and the rest into heat. If this heat is not dissipated adequately, LEDs can heat up and even cause irreparable damage. In less serious cases, a high junction temperature in an LED can cause a reduction of light emission, colour changes and/or a significant reduction in its working life. Heat dissipation is therefore a key factor in the correct function of a light fixture. It is achieved through the management of various factors, namely:

  • Circuitry printed on the PCB
  • Correct heat transfer from the PCB to heat sink, determined by choice of PCB material and thermal interface between the PCB and heat sink (e.g., thermo-conductive adhesive strip)
  • Heat sink design appropriate for light fixture performance: the metal part of the appliance, due to its thermal conductance, dissipates heat into the air around the LED thanks to the temperature differential.
ADVANTAGES OF LEDS OVER OTHER LIGHT SOURCES
  • Energy saving
  • Greater reliability and working life
  • Mechanical and thermal toughness: resistance to shock, vibration, and high and low temperatures
  • Instant lighting at full power
  • Small size, enabling light sources to be housed where once it was impossible
  • Coolness (no direct emission of radiant heat)
  • Supplied by low tension direct current and therefore electrical safety for user
  • Lasts up to 50,000 hours if good quality and correctly heat sunk

Units of measurement

VOLT (V)

V = J/C = unit of measurement of ELECTRIC POTENTIAL

AMPERE (A)

Unit of measurement of INTENSITY OF ELECTRIC CURRENT (the amount of electrical charge that passes through a section of a conductor per unit of time)

WATT (W)

= J/s  V x A = unit of measurement of ELECTRICAL POWER