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Candela (cd)
The standard unit of luminous intensity. It comes from the English word "candle " , and it is approximately equal to the brightness of a candle fire, or approximately 12.56 lm ( 1 candela multiplied by the full spherical angle) .
Light intensity (lm/sr)
The light volume emitted per unit angular ( lm / sr or why ) . This parameter determines how bright is a light source..
Luminous slux (lm)
The total amount of light emitted by a light into the space around the body, measured in lumen. For example, 1500 lm means that the light radiates 1500 units of light (lumens). This parameter, however, says nothing about the distribution of these lumens (whether it is focused or spherical), which determine by other parameters.
For example, for a luminescent lamp emitting 1700 lumens in all directions (4pi, or full solid angle), the brightness is 135cd . On the other hand, if the same amount of light is focused in a 20 degrees conical angle, the intensity will be around 18000cd .
Surface illumination (lx)
The amount of light that falls on the specified surface area (lumens / square meter) . Surface lighting is a useful parameter for roughly assessing the lighting system - it can tell if there is generally enough light in the room, and whether this amount of luminaire is roughly enough to fulfill specific criteria.
Vertical surface illumination (lx)
A parameter that is little discussed in everyday application – It describes, for example, how well the athlete will be lit up in front of TV cameras, or how smooth or have contrasting wall or object scene.
Uniformity / Contrast Ratio (x:1)
Shadows play an important role in our subjective feelings about a place – they create contrast. Exhibitions use contrast to highlight items of value. Household lighting utilizes shadows as accent techniques - to make the room more engaging and pleasant to inhabitants. It is worth mentioning that this parameter is included in most of the lighting standards, and studies have been conducted, which shows that inadequately low or high contrast rate has an adverse impact on human perception of objects and spaces.
Power supply
All systems (and not just lighting fixtures) that are unable to operate directly from general power network, need a power supply that turns the available power voltage to the desired voltage level, for example 12VDC or 2kV . These inverters and associated equipment known as power supplies, ballasts, starters, and many others are both technical and slang names.
Power Supply Efficiency
Depending on the power supply quality and type, they are able to transform general power to desired voltage levels. This transformation itself requires energy, either as resistance heat, or due to other technical reasons (thermal or electromagnetic). Power supply efficiency typically ranges from 50 % to about 98 % - it depends on the quality of the product, use, load, lighting technology, the operating mode and other parameters.
Power supply power factor correction
Parameter, which is often confused with the power supply efficiency. This parameter characterizes the power supply's ability to account for phase shifts in AC voltage and AC current; high correction factor provides for low reactive power, i.e. smaller load on cables and power system. This is an important factor in high-power installations , so we rarely discuss it in everyday life.
Luminaire reflector / optics
In order to ensure that the light emitted by the light source is directed in the required direction and at necessary angle, one use reflectors or (in case of LEDs) optics. Reflector simply reflect the light outwards from the fixture, allowing more light emitted from the fixture. Optics, on the other hand, diffuses light - it helps to point light source to better disperse the light in the room. The reflectors and the optical system "eats" a part of the light - the rate can range from 3-4% to up to 50% of the luminous flux. Losses depend on the quality of the reflector or optics.
Luminaire efficiency
This parameter tends to be described by lm/W , i.e how the luminaire emits light per one watt of consumed power . It is important to know whether the manufacturer / dealer indicates the energy efficiency of the light source, or the entire luminaire. Given that the loss of the luminaire luminous flux can reach up to 50%, a wrongly specified efficiency value can lead to misleading judgment.
Light system efficiency
Lighting designers often use the system energy efficiency indicators, which consists of light fixtures efficiency coupled with its utilization coefficient. Good light designer will ensure that the same installed capacity could reach a much lighter, more adaptable and energy efficient solution. To achieve this, professional lighting fixtures, their correct positioning, and other factors should be taken into account.
CRI index
Light quality directly affects the ability of a light source to emit light waves in the widest possible visual spectrum. If the luminaire emits only certain waves (as is the case with low-voltage yellow street lamps), the human eye is unable to distinguish between tones. This may not be essential in street lighting (one only needs to see obstacles, not its true color), however it is very important in retail industry – products must be presented in their best shades. CRI index ranges from 65 to 98 (100 is the theoretical maximum determined by the spectrum of incandescent bulbs).
Color Temperature
Designers and clients call it "warm or cold white light". The technical term for it is Kelvin (for example , 3000K ), which represents the dominant light source electromagnetic waves - " warm range " ( 2500K - 3000K ) is dominated by a red hue, while "cold range" ( 4000 - 7000K ) is dominated by a blue hue. Today, almost all light technology allows you to select the perfect shade - 2700K or 4000K house for office. This is a crucial factor determining the character of space, and allows you to define the functional space dominance.
Luminaire life
Durability consists of three main components – durability of the body of the fixture, service ife of the bulb and power supply. The highest combined lifetime is boasted by gas discharge lamps and LED lamps, lower - fluorescent light bulbs , while the smallest goes to halogen lamps and incandescent lamps.
Luminaire IP/IK class
In accordance with the EU standards, these two parameters stand for luminaire fixture protection from the world hazards: IP class determines the luminaire resistance to penetration by water and dust caused, IK class – protection from direct vandalism. The parameters rangef IP00 to IP68 , IK00 to IK10.
Light Perfomance calculation
Lighting designers must verify that their envisioned lighting system will perform admirably after installation – well lit premises, engaging contrasts, etc. They have a number of tools that allows them to simulate the expected results – visual rendering allows to correctly identify blind spots, excess light, or other possible flaws in the design.
