Ballast lumen factor BLF (%)
Refers to the ratio of light output from the lamp on emergency operation to the nominal light output.
Indicates how broadly the light is emitted from a reflector lamp. It can be thought of as an imaginary cone whose apex intersects the lamp face, and the breadth of the cone extends outwards to the point where luminous intensity has diminished to 50% of the centre beam value.
The term binning refers to the variations which occur within a single production batch of LED’s such as chromaticity, lumen output and forward voltage. It is important that a specific bin has been identified and selected to ensure a uniform and constantly even lighting installation is achieved. If all the LED’s were selected from one production batch and used in the same luminaire or installation, there would be a mix of colour temperatures and brightness levels. For the lighting manufacturer / designer binning is an essential part of LED specification.
MacAdam ellipses methodology was created in 1943 for mathematically constructing ellipses around target points, something which became very useful for the lamp industry. ANSI C78.377 is now the standard for chromaticity specified by the American National Standards Institute. ANSI recommends that lamp manufacturers stay within a “4-step” ellipse. This means that, given a certain target point on the CIE diagram, manufacturers are given a fairly wide range of perceptible differences.
The unit of measurement for luminous intensity, which refers to the quantity of light emitted in a particular direction. The symbol is cd.
Colour Correlated Temperature (CCT)
An incandescent light bulb is very close to a perfect black-body radiator, so its colour temperature is basically the temperature of the filament. However many light sources, such as fluorescent tubes or high intensity discharge lamps, emit light by processes other than thermal radiation and therefore it is not possible to apply the black-body spectrum. For these light sources it is possible to assign what is known as a colour correlated temperature (CCT). The CCT is the colour temperature of a black-body (Planckian) radiator which most closely matches the colour of the light emitted from the lamp.
Colour Rendering Index (CRI)
The colour rendering of a light source is an indicator of its ability to realistically reproduce the colour of an object. The chart illustrates our ability to accurately determine colour depending on the colour rendering properties of the light source. The higher the colour rendering index (on a scale of 0 to 100) of the source the better our ability to perceive differences in colour, which is a considerable aid to highlighting fashion products and effective display of coloured artworks.
The CIE colour rendering index (CRI) is a method to determine how well a light source’s illumination of eight standardised colour patches compares to the illumination provided by a reference source. At Ra (8) the perceived colour shift of eight reference colours is measured as a percentage and averaged to give one number. However it is currently understood that due to the spectral power distribution of LED’s that instead of using the standard Ra8 it is important to include 7 additional colours which include red, yellow, blue & green and use Ra14 to ensure better results.
Colour temperature is a characteristic of visible light that plays a significant role in lighting applications. The colour temperature of a light source is the temperature of a perfect black-body radiator that radiates light of a similar appearance to that of the light source. The colour temperature is measured in units of absolute temperature; Kelvin (K).
Colour temperature works paradoxically to our cultural associations with colour, red as hot and blue as cold. On the black-body curve, blue occurs at higher temperatures than red. A good example is a candle which has a warm red orange appearance but in fact has a low Kelvin temperature, 1850K. Therefore higher colour temperatures (5000K more) are called cool colours (blueish white); lower colour temperatures (2700 – 3000K) are called warm colours (yellowish white through red).
The Planckian locus shows the chromaticities of black-body light sources of various colour temperatures and lines of constant correlated colour temperature shown within the CIE chromaticity diagram
The SAKAR lamps range includes dimmable LEDs lamps. Most conventional dimmers have been designed for incandescent lamps and are therefore rated for higher minimum loads (W) than LED lamps consume. There may therefore be some restrictions in terms of functionality of dimmers with individual LEDs – but when more than one lamp is used to increase the total loading, dimming becomes easier.
Downward Flux Fraction (DFF)
The factor of the total LOR, which is downward, taking the combined ULOR and DLOR as 100%. Using Cassini as an example, the DLOR is 37% and the ULOR is 15% so the combined is 52%. If this is taken as 100% LOR, 72% is downward (37% divided by 53%).
Electronic devices that transform the high mains voltage into a constant current lower voltage for operating the LEDs. A miniature electronic driver is contained inside the base of each SAKAR LED lamp.
Glare is the discomfort caused by high luminances in the field of vision.
A device used to conduct heat away from the LED sources and dissipate it to the surrounding air. The more efficiently an LED is cooled the greater its efficacy, light output and lifetime. Materials having excellent thermal properties and optimised cooling fin geometries are engineered into SAKAR lamps and luminaires to deliver the pinnacle of performance.
Infrared (IR) Radiation
Comprises electromagnetic waves in the spectral range between visible light and microwaves, which produce a heating effect when absorbed by materials. All lamps and luminaires produce infrared radiation, but the quantity emitted by LEDs is far lower than other technologies and this makes them ideal for reducing air conditioning load, as well as for the illumination of heat-sensitive goods.
This definition determines the amount of light that covers a surface. If Ø is the luminous flux and S is the area of the given surface then the illuminance E is determined by E=Ø/S. The unit of illumination in SI system is lx, and in foot-pound system it is foot-candle. One lx is the illuminance of 1 m² surface area uniformly lighted by 1 lm of luminous flux.
Junction Temperature (Tj)
The temperature of the Junction of the LED die inside the LED lamp. Measuring the LED die temperature by direct mechanical means is difficult and may lead to erroneous results. It is recommended that the Tj is calculated with manufacturer’s data through measurement of the temperature at the solder point (Tsp).
LED (Light Emitting Diode)
An electronic semiconductor component which emits light when an electrical current flows through it. The colour of light emitted depends on the chemical doping of the semiconductor material.
An optical component having two refractive surfaces, at least one of which is either convex or concave. In LED lamps the function of a lens is to focus or disperse the light rays to achieve the desired beam angle or light distribution pattern.
LED lamps can have extremely long lives, however their light output diminshes as they age. They can carry on working until they are emitting less than 10% of their initial light output, but with so little light left they would be practically useless. SAKAR defines the lifetime of its LED lamps the same way as for other lamps: i.e. the burning hours until the light output has decreased to 70% of the initial value, or when 50% of a group of lamps will have failed – whichever is the soonest. The International Electrotechnical Commission (IEC) is currently preparing an international standard based on similar threshold values.
Light Electromagnetic radiation with a wavelength between 380-780nm. Ultraviolet light has a wavelength of less than 380nm whilst infrared light’s is greater than 720nm.
The incidence of light flux on a surface per unit of area, measured in lux. There is a difference between the vertical and horizontal lighting level.
Light output ratio (LOR)
The ratio of the luminaire light output to lamp light output. The efficiency of the luminaire.
Unit of luminous flux used to describe a quantity of light emitted by a source or received by a surface.
Rated Lumen Maintenance Life (Lxx): The elapsed operating time over which the LED light source will the percentage, xx, of its initial light output.
- L80 = Time to 80% lumen maintenance, in hours
- L70 = Time to 70% lumen maintenance, in hours
For LED lamps and luminaires, lumen maintenance is often shown as curves of relative lumen output over time for the LED under various operating conditions, such as drive current and junction temperature.
How well a luminaire uses the luminous flux of the lamp(s) employed. This ratio is calculated by dividing the total luminaire lumens by the total circuit watts.
The measure of brightness with which the eye perceives an illuminated surface from a certain direction. The luminous intensity per unit of visible surface of a light source (direct) or an illuminated surface (reflection). Luminance is indicated in candelas per square metre (cd/m2).
Luminous efficacy (lm/w)
Indicates how efficiently a light source converts electrical energy to light.
Luminous flux (lm)
The total light output of a light source measured in lumens.
Luminous intensity (cd)
The power of a source or illuminated surface to emit light in a particular direction, measured in candelas.
The unit of illuminance, equal to one lumen per square metre (lm/m2).
Shows whether the luminaire emits a narrow or wide beam of light and indicates the lighting level measured at the centre of the beam. The beam diameter and angle indicate where half the illuminance is measured in relation to the centre of the beam. It gives only a rough guide of the size of beams narrower than 40°.
The graphic representation of the luminous intensity in different directions. If two curves are plotted, the distributions are in two vertical planes. The value is indicated in candelas per 1000 lumen (cd/klm) and therefore must be multiplied by the nominal luminous flux of the lamp(s) used. The polar curve graph also indicates luminaire efficiency.
SAKAR lamps and luminaires are extremely durable and do not contain any mercury, lead or other toxic metals. However because their drivers contain electronic components they must be disposed of as waste electrical and electronic equipment at the end of their life.
An optical component having a mirror surface, which captures light rays from the source and bounces them back at a particular angle. Although more commonly used in incandescent and halogen lamps, some SAKAR LED lamps use reflectors to control their light instead of a lens.
Room index K
An index relating to the dimensions of a room influencing the amount of light emitted from the fitting onto the working surface.
where: a = room length b = room width h = height between the luminaire and working surface
Shielding angle (º)
The horizontally measured angle from which the lamp or reflection from it in the reflector is no longer visible. It is an important measure of glare and, therefore, light comfort.
Spacing to height ratio (SHR)
Used to determine the maximum distance between luminaires. The ratio of the distance between adjacent luminaires to the the distance between the luminaire plane and the horizontal working plane.
LED lamps cannot be switched on and off indefinitely, but are rated to tolerate an impressive 60,000 switching cycles or more.
TCO (Total Cost of Ownership)
TCO includes all the costs over the entire life of a lamp or for a particular operating time. It covers procurement costs, electricity consumption costs, relamping costs and may even incorporate a reduction in the necessary air conditioning load. LEDs are presently more expensive to purchase than lamps based on other technologies, but their minimal energy consumption results in rapid payback when replacing incandescent and halogen lamps.
A device for reducing the high mains voltage down to a lower voltage. A distinction is made between conventional (magnetic) transformers and electronic transformers. SAKAR low voltage LEDs will function on all magnetic transformers, and compatibility details with electronic transformers are available in the technical data sheets.
Uniformity ratio of illuminance
This indicates the degree of evenness of the light on the working surface and is shown as a ratio of the minimum to the mean lighting level on a surface. The lower the number the more disturbing the light.
Ultra Violet (UV) radiation
Comprises electromagnetic waves in the spectral range between visible light and X-rays, which are invisible to the human eye but essential for all life (delivered via natural sunlight). Small amounts of UV are emitted by many light sources (e.g. Halogen and Discharge) and over time will cause fading of coloured objects being illuminated. SAKAR lamps and luminaires do not emit any UV radiation.
The ratio of the light flux which the reference surface receives to the totalled luminous fluxes of the installation lamps. This is influenced by the shape of the room and selected luminaire and is expressed in the form of UF tables.
The derived SI unit of electrical pressure (symbol V). Low voltage LED lamps (12V) operate with transformers. High-voltage LED lamps can be operated directly on the mains supply (220-240V).
Watt is the SI unit of power and was used for incandescent lamps as an indication of their light output. Since modern energy saving lamps and LED lamps consume far less power to achieve the same brightness, however, the wattage is no longer as meaningful. The lumen value is now used instead.
Wattage Comparison According to ErP
The EU directive for nondirectional light (ErP DIM I) requires a certain luminous flux from LED lamps to make a comparison with incandescent lamps.