Light color - Kelvin
Does white light have a color? No, it is a
multicolored light and therefore white. But we know differences of
white light. Fluorescent is commonly known to us as cold white
light, however, incandescent light is known as warm white
light.
LEDs offer a wide range of white light colors. You can choose from warm white
like incandescent lamps to cool white like polar sunlight.
3 main groups of luminaires are typical:
- warm white = ca. 2000-3200 Kelvin
- neutral white = ca. 3300-5300 Kelvin
- cool white = 5300 and> Kelvin
In order to establish standardized values, physics has devised a theoretical black spotlight that changes its color from red-yellow to white and blue when heated. A scale has been derived from this, which is used as the unit of measurement Kelvin (K).
A draft flame image gives us a simple idea for the color temperature. At a lower temperature it is yellowish red, at a higher temperature it becomes
bright white to slightly bluish.
Color rendering index (CRI) Ra
CRI is an abbreviation for "Color Rendering Index" and means a color rendering index, which is given in Ra.
Color
rendering describes the relationship between the color stimulus and the color impression.It is therefore a matter of reproducing the colors of objects that are illuminated with different
light sources and then compared with a reference light source. On the one
hand, a black spotlight with a color temperature of up to 5,000 Kelvin and, on the other hand, a light with a spectrum similar to daylight over 5,000 Kelvin serves as a
reference.
A Ra 100 is the best
color reproduction = no deviation from the ideal template, the colors of the illuminated object appear as in nature.
In work areas such as offices only lamps with a color rendering index of at
least Ra 80 should be used. All rooms in which
color perception is important need the highest possible color rendering index (i.e. Ra 90 upwards).
With fluorescent lamps,
the Ra value is often encoded on the lamp.
Example:
The printed value 850 means a Ra value of at least 80 (850) with a color
temperature of 5000 Kelvin (850)
Luminous flux
The total luminous flux,
or better understood the entire amount of light emitted from a light
source, whether of round emitters such as incandescent lamps, fluorescent lights, or
halogen lamps, is expressed in lumens.
Thus, this size is the only comparison metric for better or worse bulbs.
But if you look for the energy efficiency of a light
bulb, then "lumens to watts" is important.
Candela
In light emitters such as halogen lamp or reflector lamps, the axial luminous
intensity in candelas is often given.
This value is important where all that matters is brightness
in the center of the emitted light cone and not to
speak in an efficient lighting of the room.
An example of this is a punctual highlight of goods in a bottom-lit store. Also inefficient LED
Spotlight (lumens / watt) can generate high candela
values when the light is strongly directed to the axis.
Lux
The illuminance in lux
(lx) is the quotient of the luminous intensity of a point source of
light in candelas (cd) and the square of the distance in meters (m). Thus, the illuminance gets a quick reference
when a single light source is considered such. As with artificial lighting. Conversely, the brightness outdoors has virtually
nothing to do with distances, since the light source is practically
infinite (for example, cloud cover).
The light intensity is measured with the lux meter or calculated in simulations such. As to determine
whether a work surface is sufficiently illuminated. You can find
instructions in countries Committee on Occupational Safety and Health
(LASI).
Beam angle
The light beam angle of a lamp can be seen clearly with the naked eye only focus lamps.
There, the clearly defined beam of light is unique. For all other lamps and lamps as
the eye can only distinguish general and in very strong dependence on the ambient light of the observation space. The beam angle describes only a guideline for many LEDs. If the LED has an internal or external
optical enlargement or alteration, the beam angle can differ considerably.
Where a
plurality of light bulbs built close to each other, the light at places where overlap several circles of light could be particularly intense. LEDs without optics stem are therefore better suited for such bulbs. As this intense light the center and the edge leaves the light intensity according to
uniform. LED bulb with a higher
luminosity as power LEDs or LED hight lumen compared to standard incandescent lamps or LEDs - generate a very strong light.
What is a lumen to watt?
The light output of a
lamp is measured in lumens. Under light flux is defined as the
total in all directions from the light source in the room emitted visible light. Watt electric power and has served
as a parameter for the power consumption of a lamp. This has changed
with the energy efficiency of new bulbs. The
sale of the luminous flux for all lamps is specified as a parameter,
in addition to the first wattage. The lumen on the
package is rule in the european Union since 01 September 2010. The lumen value shows the comparison of
lamps.
Example:
As a replacement for a 15 watt incandescent light (136 lumens)
an LED bulb with about 3 watts is recommended. Now,
since the number of lumens must be stated that the consumer can orient it even now. This ensures that the LED lamp is as bright as the incandescent lamp replaced.