A Matter of Lumens

LED bulbs, talk about Lumens, not watts

As discussed in previous articles, the use of LED technology has given way to change the chip and stop thinking about watts when choosing a light bulb. Let's think lumens to choose the degree of luminosity that we get with our lamps. Instead of speaking in terms of power, we talk in terms of brightness, which is really what we want from a bulb.

What are the Lumens?

The lumens represent the actual amount of light (luminous flux) from environmental light source. The greater the number of lumens, a room is brighter. But the problem remains, how many lumens need to illuminate my room?

The lighting level is measured in a unit called lux (lx). This unit is derived from another, called lumen, which is the measuring luminous flux. An amount of illumination 1 lux equals 1 lumen per square meter. That is, if a room is illuminated by a light bulb 1,000 lumens, and the surface of the room is 10 square meters, the illumination level of 100 lx. To determine the light in a room, used a device called a light meter. Considering the amount of lux as required, should take into account the height of the light source and its luminous flux, after which, according to the formulas of lighting, it is determined that luminous flux shall have the lamps.

We can see how bulbs that have the same power emit more or less lumens, each manufacturer achieves a different amount, but the relationship becomes between 70 and 90 lumens per watt. Currently the most representative value is around 90 lumens / watt, although there are high quality bulbs (dichroic) with values ​​ranging up to 110 lm / W. So although we should not, it seems we again rely on the wattage bulb to find out we need, but is simply a review to understand how the relationship works. Compared with the incandescent bulb the relationship usually follows, with smaller varieties for manufacturer.

The difference in lumens provided by each LED bulb is due to the thickness of the phosphor layer covering the LED or chip. We can distinguish two situations when the phosphor layer is thick (with a color yellow-ocher ) bulb emits light that can be defined as warm , while when the layer is thin (colored pale yellow ), we need the light that is emitted is called cold light .

However, the performance also depends on the later type of lamp where the bulb and its color is installed.The lower dispersion of light in LED bulbs with less lumens makes illuminate more than other types of light bulbs with more dispersion.

LED bulbs, A Matter of CRI and CQS

LED bulbs, a matter of CRI and CQS

One aspect that has introduced LED bulbs technology is the emergence of a new jargon in our vocabulary, although no terms were already very familiar, as they could be " lumens "or" kilowatt hour ", there are new concepts we have to know and understand.

In this article we will focus on two of them, which are the Color Rendering Index - CRI (CRI English: Color Rendering Index) and Quality Chromatic Scale - ECC (English CQS: Color Quality Scale).

The CRI

The CRI measures how colors appear under the illumination source, compared with a reference source that has the same color temperature.

What comes to mean a roughly is how accurate is the reproduction of a color, a numeric value classifies the color quality produced by a light source. If incandescent bulbs are taken as the reference point (have the value 100), while an LED bulb quality is estimated to be about 80 at least. This CRI 80 is what the manufacturers listed on the packaging of their products.

Why the value of incandescent bulbs or the sun is taken, it is because they emit light in all directions within the visible spectrum and this does not happen with compact lamps (CFL) or LED.

Is it enough a CRI of 80?

For general for everyday use in our homes is the appropriate value. Higher values ​​are converted to other areas such rooms would be art exhibitions and similar centers. In contrast, values ​​below 80 make colors appear duller and yes are a not recommended choice.

CRI test is based on an average of eight colors pastel (little saturated), for the classification. This would mean that even if a bulb playing a couple of colors at a low value, the CRI can still remain high as long as these colors are not bad played one of 8 colors that are averaged.

LED bulbs can reproduce faithfully bright colors (saturated), but not always pastel colors, which can be misleading the CRI in this type of bulbs.

The CQS

To overcome the shortcomings hauling CRI LEDs method has been developed color quality scale as an alternative method. CQS considers a number of factors when trying to define the way a light source reproduces color. These include the chromatic discrimination, human preference and color rendering (the method evaluates 15 colors more accurately cover the range of normal colors of an object).CQS factors focus a little less on color fidelity and more on perception.

In future articles we will increase the vocabulary while we explain the most common concepts that we find in the printed features packages of this type of bulbs.