Lighting Terms

Lumen (lm)

Lumen is generally known as the unit of luminous flux. This unit comes from any light source and is evaluated according to the spectral sensitivity curve with the help of the normal eye. The lumen value is measured with the help of a special device called "sphere".

Lux (lux or lx)

Lux, the unit of brightness, is a term used to express the light intensity on a surface. For example; If the luminous flux falling on a 2 m² surface is 2 lm, the illuminance (level) occurring on this surface is 2 lux or 2lm/m². In addition, the amount of brightness is not related to the surface. Regardless of the amount of reflection of the surface, the amount of brightness depends on the intensity coming from the amount of light. Therefore, devices called Luxmeters are used to measure this amount.

Candela (cd)

We can say that Candela, which is the unit of luminous intensity, is the intensity of a point light source that emits uniform light in every direction and transmits 1 lm of luminous flux at a space angle of 1 steradian. 

Light Angle (Degrees – °)

It shows the direction in which it effectively spreads from a light source. In this direction, all lights and light sources, except for LED lighting, emit light in every direction. However, these light sources can be controlled by using certain reflectors. For example; 10° ≈ 45° = Accent Lighting 60° ≈ 120° = General Lighting

Watts (W):

Watt, known as the international standard unit of power, can be used when a current of 1 ampere (A) flows at an electrical potential of 1 volt (V).

CIE

CIE is an international organization formed by the initials of the words "Commission Internationale de l’Éclairage" and known in English as the "International Commission on Illumination". CIE is an organization that is concerned with determining standards and conducting research on light, illumination and color.

Light Pollution

It is the name given to the amount of light that causes wastefulness, hinders astronomical observations and also endangers natural life due to the excessive spread of light into the environment.

Space Angle

It is the name given to the pyramid or cone shaped space through which partial light passes. Its unit is steradian (sr).

Light Dispersion Curve (Polar Photometry) 

A light distribution curve or polar photometry curve is a graph that shows how intense the light of a source is in a particular direction or how much energy it carries. These curves are used to visualize how the light of a source is distributed in a particular angle or direction. In particular, they are used to study the light distribution of a lamp or other lighting device on a surface. These curves show the intensity of light or the luminous flux at a particular angle or direction.

Upper Half Space Luminous Flux Ratio (ULOR)

A measurement used to determine the upward light emission of luminaires. This term expresses the ratio of the amount of light emitted by luminaires in the upper half space to the total luminous flux.

Lower Half Space Luminous Flux Ratio (DLOR)

It refers to the ratio of the amount of light emitted by lighting fixtures in the lower half space to the total luminous flux. This term is used to measure and evaluate the amount of light emitted by lighting fixtures towards the ground or work area.

Degree of Protection

It is a term expressing the resistance of lighting fixtures against dust, humidity and water. This term is expressed internationally with the code IPX1X2. The first digit (x1) in the protection value indicates the degree of protection against solid objects, and the second digit (x2) indicates the degree of protection against water.

Economic Life

Bir lambanın 100 saat kullanım sonrasındaki, toplam ışık akısındaki lambaların kullanılmaz hale gelmesi ve ışık akılarındaki azalmalardan dolayı yaklaşık %30 değer kaybettiği sürede geçen zamana denir.

Light and Radiation:

“Light” describes a form of electromagnetic radiation that lies within a specific region of the electromagnetic spectrum and can be detected by the human eye. Generally, visible light includes colors such as red, orange, yellow, green, blue, and violet, which make up the colors of the rainbow, as well as white light. However, other parts of the electromagnetic spectrum also include types of light such as infrared, ultraviolet, x-rays, and gamma rays. “Radiation” refers to electromagnetic waves, which are the carriers of energy emitted from a source. Radiation is the process of propagating waves of electromagnetic energy from a source into the environment. Light can be emitted from many different sources; For example, natural light from the sun, artificial light from lamps, lasers, LEDs, and other artificial light sources.   In short, the term “light” describes radiation in a specific region of the electromagnetic spectrum, while the term “radiation” refers to the process of transporting and propagating this electromagnetic energy emitted from a source.

Color Temperature

A measurement of the color tone of a light source when observed. Color temperature is measured in units of Kelvin (K) and represents the degree of warmth of a light source's color as perceived by the human eye. Color temperature is often thought of as a measure of warm and cool colors. Lower color temperatures (for example, 2700K – 3000K) represent a warmer, yellowish color of light, while higher color temperatures (for example, 5000K – 6500K) represent a cooler, bluer color of light.

Light Color

Light refers to the color characteristics of the light emitted by the source. Light color indicates the visible color spectrum of light and is usually based on a specific color temperature or wavelength. We can generally examine light color in 3 categories. These are; Warm white, Natural white and Daylight white.

  • Warm white < 3300 K (ww)
  • Natural white 3300-5000 K (nw)
  • Daylight white > 5000 K. (tw)

Color Rendering

Color rendering index, also known as “color rendering index,” is a measurement that measures how much a light source contributes to the accurate perception of true colors. This index evaluates the ability of a light source’s spectrum to accurately reflect the true colors of objects. For example, the color rendering index takes a value between 0 and 100. A higher color rendering index indicates that a light source contributes more to the perception of true colors. 100 is an ideal color rendering index, representing a light source that accurately reflects true colors.

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