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What is LED light, Kelvin, Lumens, Ra
ODSIF Intelligence Made Easy

What is LED light, Kelvin, Lumens, Ra?


LED stands for Light Emitting Diodes. They have been known for a long time and used in various devices such as indicator like in hi-fi equipment, coffee machines, cars, household appliances, but it is not until recent years that the brightness from them has become so powerful that they could be used as light sources. LED can shine in many different colours, but can be categorised by being only able to shine in one colour at a time. The colours, which are easiest to make on LED are blue, yellow, green, and red. The white colour cannot be made with an LED directly. What light producers do is to make a blue diode and then let the light pass a phosphor layer, which changes the blue colour into white. With the three LED basic colours red, green and blue, it is possible to make all colours in the colour spectrum. This is used in all colour TVs, where all colours are created from these three LED basic colours. An arbitrary colour is made by mixing the RGB colours in different intensity together. Typically, each of those three basic colours has 256 light levels and the number of colours amount to 16.8 million (256x256x256).

Colour temperature

The colour temperature is a measurement of the colour of the light itself. Colour temperatures over 5000K are called cold colours and colour temperatures, lying under 3000K, are called warm colours. the more there is of the red colour, the warmer the light gets. As example the old incandescent bulbs are as low as 2500K and halogen bulbs a little higher or around 3000K. LEDs are available in many different colours, all from around 2700K, which some producers call VWW (Very Warm White) and then the typical WW (Warm White), which lie around 3000K and White, which may lie much higher or up to 6000K.

RA (or CRI)

RA value is the ability of the light to reproduce colours from the material or the things falls on. The less RA value the poorer the light is to reproduce colours from the material or the things, the light falls on. An old-fashioned incandescent bulb and a halogen bulb have a RA value, which is close to 100, which is the optimum colour reproduction. An incandescent bulb contains all light colours and can therefore reproduce all colours. In a colour TV where all colours are made from red, green and blue colour, all colours can be made, but since these colours are all made from the three LED basic colours, they cannot reproduce all colours, which the light falls on. Therefore, at white light, which has been made by these three LED basic colours, will have a very low RA value or down to about 20.


lm or lumens tells how much brightness comes from the light source. The bigger value the higher brightness. Before the LED time one might say that the brightness was more or less expressed in Watt. One went out to the store to buy 40W or 60W bulbs, which were the most common sizes. But for other purposes, it was possible to buy from e.g. 10W to 200 W bulbs. Now, that we have got LED and high-efficient halogen light sources, it does not make sense to talk about watt any longer. The new expression for the brightness of light sources is Lumens. The old 40W bulbs gave around 450 lumens, whereas the 60W bulbs gave around 800 lumens.

LED lifetime

The lifetime of LED is much longer than the old incandescent bulbs or from 10-25 times longer. The old incandescent bulbs have a lifetime of approx. 2000 hours, whereas LED has a lifetime of approx. 20.000 - 50.000. However, it should be mentioned that the lifetime of the LED are calculated so that when the light from the LED has fallen by 50%, it is the lifetime of the LED in question. The lifetime of the old incandescent bulbs was calculated until the bulb did not shine any longer. The lifetime of LED is strongly dependant of the cooling of the LEDs. All ODSIF's lamps have a big cooling surface of aluminium ensuring that the LED can lose heat, and therefore have a lifetime of 50.000 hours. What does that mean in years? Well, if you use the LED light for 4 hours a day on average, the LED light will last for 34 year. So there is a rather big chance that a lamp will be scrapped before the light from it has become useless.


lm/W tells how much of the power the light source is converted to light. The higher value the better. The old incandescent bulbs had a very low utilisation or from 5 through 12 lm/W. Halogen bulbs have a higher utilisation or around 17 - 25lm/W. LED have an even higher utilisation or from 50 thought over 100 lm/W. The theoretic limit for LED lies around 300 lm/W. This means that when the limit has been reached, you can by using 1,5W LED reach the same brightness as the old 40W incandescent bulb. A good rule of thumb is that a brightness of approx. 450 lm corresponds to a 40W bulb and a light of approx. 670 lumens corresponds to a 60W bulb.

ODSIF's way of making good and pleasant colours

To make the white light, we use a white diode as main light source. Our white diodes are quality diodes with a CRI value of 80 or more and a colour temperature of under 3000K. Thus our light is a soft and pleasant light with all the necessary colour components to be able to reproduce colours from the material or the things, on which the light falls. To tone this light, we use RGB quality diodes from among others OSRAM. We tone the light by mixing the colours from the RGB diodes together with the white light. That way we maintain the high CRI value and can make light with different light nuances. E.g. when we make a golden light, we mix the white light with a strong red colour, a little green colour and very little blue colour.

Temperature of different light sources
RA value of different light sources
Brightness in lumens of different light sources

LED lifetime in hours

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