Basic Information


Lumen (lm):

It is the unit of luminous flux. Luminous flux means the energy flux coming out of a light source and assessed according to the spectral sensitivity curve of normal eye. The total lumen a light source has is measured with special equipment called “sphere”.


Lux or lx:

Lux is a unit of illuminance level. It is used to express the light intensity on a surface.

Illuminance (level) can be shortly described as the luminous flux per unit area. If the luminous flux concentrated on an area of 1 m2 is 1 lm, then the illuminance (level) on the surface is 1 lux or 1 lm/m2.


The illuminance (level) on this surface does not depend on the type of surface. Without regard to the reflection feature of the surface, for example whether it is black or white; the illuminance (level) depends only on the intensity of the luminous flux concentrated on the surface.


A light meter called Lux Meter is used to measure the total luminous intensity on a surface.


Candela (cd)

It is the unit of luminous intensity. We can say that the luminous intensity of a point light source which emits light in a proper way according to each direction and which conveys luminous flux of 1 lm through a spatial angle of 1 steradian is 1 cd.


Luminance (cd/m2 or Nit)

Luminance concerns the luminous intensity of a light source affecting the eye. If the light source is a primary light source, then this intensity is in direct proportion to the luminous intensity “I” in the observation direction of the source and in inverse proportion to the observed area “Sg” of the source that generates this intensity. The luminance of a surface which generate luminous intensity of 1 cd in a particular observation direction and whose projection (observed area) on the plane vertical to this direction is 1 m2 is 1 nit (cd/m2).


The luminance of the secondary light sources is a function of the illuminance (level) on these levels and the multipliers of light reflection or light transmission. If the illuminance (level) on a visible surface is 1 lux (lm&m2), the light reflection or light reflection multipliers of the surface and the division of the multiplication to “ “ number gives the luminance as 1 nit (cd/m2).


Light Beam Angle (Degree - °):

Light beam angle demonstrates the direction to which the light beams are actively emitted from a light source.


All the light sources with the exception of LEDs emit light to all directions. However, these light sources can be arranged in a way to control the light beam angle by using certain reflectors.


10° ≈ 45°    = Accent Lighting

60° ≈ 120°  = General Lighting


Color Temperature (Kelvin or K): Color temperature demonstrates the color of light of a light source which emits red radiation. Usually the old type incandescent bulbs have a light color of 2500K. Apart from that, 2700K means yellow light, 3000K means daylight (or warm white), 4000K means neutral white, 5000-6500K means cold white.


Color Rendering (CRI - Ra): Color rendering is defined as the proportion of the visibility of the things to their similarities to their effects under the sunlight for 8 different colors of a light source, determined by the standards. They are demonstrated in values such as 80-90. Generally; the higher the value of the CRI is, the easier it is to correctly perceive colors.


Watt (W): Watt is the international standard unit of power. One watt is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt.