Basic lighting technical terms

  • Light: light is a radiant energy that can be sensed or seen by the human eye. Visible light is measured in lumens.
  • Lumen: A measure of luminous flux or quantity of light emitted by a source.
  • Luminous flux : Total output of a light source is luminous flux, which is measured in lumen.(lm)
  • Luminous Efficiency: The ratio of supplied energy, which converted  to light is luminous efficiency. lm/w
  • Illuminance : The density of light (lumen/area) incident on a surface i e the light level on a surface. illumination is measured in foot candles or lux.
  • Foot candles(fc): A  unit of illumination or light falling on to a surface. It stands for the light level on a surface one foot from a standard candle.1 foot candle = 1 lumen per square foot.
  • Lux: A unit of illuminance or light falling on to a surface . One lux is equal to one lumen per square meter.
  • Illuminance meter: A device that measures the illuminance at a location calibrated either in foot candle or in lux. Also it’s known as light meter/lux meter.
  • Kelvin(K): A unit of temperature starting from absolute zero parallel to the Celsius. 0 deg C is 273 K
  • Nanometer: a unit of wavelength equal to one billionth of a meter.
  • UV radiation: Radiant energy in the range of 100 -380 nm
  • Visible light radiation: Radiant energy in the range at about 380-800 nm
  • Glare: Feeling of discomfort produced by an object of excessive luminance.
  • Flicker: A periodic variation in light level by AC operation that can lead to strobe effect.
  • Color Rendering Index : Color rendering is the ability of light source to represent color in objects. the relative measurement of the ability is color rendering index or CRI which rates light sources on scale of 0-100.The  higher the CRI the more vibrant or closer the natural the colors of objects appear. Light from lamps with good 70-80 CRI and excellent 80+ CRI color rendering index.
  • Color Temperature: Color temperature is a numeral quantity representing the color appearance of light source . Imaging natural light from sun ,soon after rising temperature of light color becomes radish is similar to light color temperature 2700 K (warm light) When sun goes up during day time color temperature increases the light  color becomes bluish producing refreshing light like a clear sunny day which is comparable to color temperature 6400K(Day light).

2700K            incandescent white

 3000K            warm white

3500K            white

4000K            cool white

5000K           daylight

6500K           cool daylight

  • Thermal Cut out: Protection from overheating due to abnormal lamp condition.

Classification of Enclosed protection (IP)

IP 20 Standard Model.

IP 21 Drip proof ( protection against drops or liquid)

IP 23 Rain proof ( protection against rain)

IP 34 Splash proof ( protection against Splashing)

IP 44 Splash proof ( protection against splashing)

IP45 Jet proof(Protection against jet of water)

IP54Dust Proof, Jet proof(Protection against harmful deposit of dust)

IP55  Dust proof, jet proof

IP56  Dust proof, jet proof

IP 66 Dust proof ,jet proof ( protection against ingress of dust)

IP67  Dust tight , water proof(protection against immersion in water)

IP First number - Protection against solid objects

0 No special protection
1 Protected against solid objects over 50 mm, e.g. accidental touch by persons hands.
2 Protected against solid objects over 12 mm, e.g. persons fingers.
3 Protected against solid objects over 2.5 mm (tools and wires).
4 Protected against solid objects over 1 mm (tools, wires, and small wires).
5 Protected against dust limited ingress (no harmful deposit).
6 Totally protected against dust.

IP Second number - Protection against liquids

0 No protection.
1 Protection against vertically falling drops of water e.g. condensation.
2 Protection against direct sprays of water up to 15o from the vertical.
3 Protected against direct sprays of water up to 60o from the vertical.
4 Protection against water sprayed from all directions – limited ingress permitted.
5 Protected against low pressure jets of water from all directions – limited ingress.
6 Protected against temporary flooding of water, e.g. for use on ship decks – limited ingress permitted.
7 Protected against the effect of immersion between 15 cm and 1 m.
8 Protects against long periods of immersion under pressure.