Monthly Archives: October 2018

Million shades of white LED

Nowadays LEDs have great efficacy and lifetime. They produce more and more light with less power. I think that it’s less important to increase efficacy because we have already reached what the market demands. What else we need from the light than a lot of lumens? In this blog post, I’ll compare the differences between white LEDs.

We all know that LEDs are available in different color temperatures. For example, Citizen 6 generation’s LEDs are available from 2700K to 6500K. They are also available in different color rendering indexes. Color rendering index simply means how well a white light source can show, or render, colors compared to sunlight. We know that the color rendering index does not always tell the whole truth (You can read more from this blog post).

Nowadays we need a light source that has good efficacy and color rendering, and it doesn’t hurt if the light source can be customized to use in many different luminaires. We want light source that brings colors vivid and alive. Also, design interiors with relaxing atmosphere.

Let’s look into what else affects the quality of light than the color rendering index and color temperature.

White without greenish tone

IMAGE: Black line in the picture is B.B.L. Red circles indicate below B.B.L. LEDs.

In some projects, we want a light source that makes white look whiter. Some LEDs may turn white into light green. Traditional white LEDs’ color temperature chromaticity is on or very near B.B.L. (Black Body Locus). Citizen also produces below B.B.L. LEDs. Their color temperature is below the B.B.L. line. As you can see in the picture, above the line is greenish colors and below the line is reddish colors. Below B.B.L. LEDs make white look pure white and it also renders red colors better. This way we can create light that doesn’t have a greenish tint.

Below B.B.L. LEDs are very popular in shop lighting and everywhere where brisk atmosphere is needed.

Read more about the color temperature from this blog post.

More attractive display with high color contrast

The general color rendering index (CRI) is defined as an average of the sum of first eight R-values. However, these first eight indexes are rather less saturated colors, while indexes R9-R12 represent highly saturated colors. This means that the same CRI doesn’t mean same color rendering.

The Citizen’s Vivid LEDs make colors seem brighter with better color contrast. The spectrum of light has been designed to have as good as possible saturation. This way Vivid LEDs can render bold colors vividly. With better saturation, you can read easier for example newspaper under the Vivid LEDs.

Below you can see a picture where Vivid LEDs are compared. The higher the bar is, the better the color renders. The comparison is done to halogen bulb (0= halogen bulb performance).

Great use for Vivid LEDs are places where good color rendering and concentration is needed, for example, clothing and cosmetic stores, art galleries, schools, hospitals, and offices.

There are two different Vivid LEDs:

  • Brilliant Vivid – Very high color contrast.
  • Natural Vivid – High color contrast.

Vivid LEDs are meant to be combined. Use Brilliant Vivid as spotlights to bring color and textures up, and Natural Vivid as base light because it has better efficacy but has still very good color rendering and contrast.

Change the color temperature of light

Everyone is now talking about “human-centric” -lighting in the lighting industry. It means that by changing the color temperature you can maximize productivity and improve concentration or create comfortable atmospheric feeling. Citizen’s Tunable White is a great solution for “human-centric” -lighting. Its color temperature can be changed freely from 2700K to 6500K. This means that you can achieve warm light like incandescent lamp and daylight with only one module. In addition to changing the color temperature, you can also dim the brightness.

Early Tunable White products have been big sized modules. Citizen’s Tunable white is as small as the COB. This means that you can make a lot of smaller Tunable White luminaires than before. The small size also gives more even light. The spots between cool and warm dies are practically invisible, which guarantee more smoothly light.

By connecting Tunable White into the right control unit, you can change the color temperature and brightness according to the time of day.

Light that gets warmer by dimming

One of the features of the halogen lamp is that when dimmed its color temperature changes warm-toned. Citizen’s Dim-to-Warm COB-LED does the same thing.

Dim-to-Warm is a COB-LED, so you don’t need any complicated special features from the driver, like two-channeling or programming features. Ordinary triac dimmable driver is enough. Dim-to-Warm COB has preset dimming curve, so when you dim it, its color temperature changes automatically just like halogen.

I hope that this blog post gives you some new thoughts for designing the luminaires. When you use any of the LEDs that I just presented to you above, you’ll get a luminaire that has more to provide than just ordinary light source. This way you can have competitive advantage.

You can download presentation about Citizen LEDs below. If you have anything to ask, please do not hesitate to contact me. My email address is and I’m always happy to help you.

Download Here