The Color Rendering Index or CRI, for short, is a one number quantification of how good (or bad) an artificial source is at reproducing colors, compared with reference standard illuminant modeled after daylight. The highest number is 100, for daylight and incandescent lamps/halogen lamps, while gas discharge lamps are between 17 and 96, with even a negative value for sodium low pressure (the yellow type used in street lamps).

It was introduced by the International Commission on Illumination (CIE) in 1974, because of the wide variation in the ability to reproduce colors with the white light emitted by the many types of gas-lamps then on the market.

Today, with over 40 years of use, the CRI index is firmly rooted in the lighting industry and among professionals. However, it has failed to gain much traction among the general public due to the fact that soon after its introduction it became not really relevant when making a purchase decision for lighting.

The reason was that most lamps were built for specific applications that required a minim CRI value so one could not go wrong with the choice of lamp.

From 2000s onward, LED technology changed this. It is the first lighting source that can be used for every application and have the full range of performance and quality level, including the ability to accurately reproduce colors. Therefore, it is imperative you choose the LEDs with the correct CRI level for your application. 

The new Color Tunable Series from Nichia are game-changing single surface, tunable white LEDs that allow the user to smoothly transition color temperature from warm white to cold white.

The series are ideal for many applications, such as commercial, retail spot lights and residential downlights. Retail stores can change the light color based on their display or objects in it. Families will be able to change the color temperature of their home to best suit their natural biological rhythms.

Nichia’s color tunable LEDs are available in the standard 757 package and chip-on-board (COB).

Nichia 2-1 Tunable White 757 LED 2700-6500K

The game changing NF2W757G-MT in the standard 757 package use a new patented technology to allow smoothly transition from warm white 2700K to cold white 6500K. The significant innovation is its ability to accomplish color tuning under a small, single light emitting surface (LES), thus achieving superb color uniformity with high color quality, up to 90 CRI. The 2-in-1 tunable white 757 enables thinner, sleeker optical designs, eliminating the need for bulky mixing chambers.

Nichia 2-1 Tunable White COB LEDs 2700-5000K

The Nichia COB 2-1 Tunable White Series are available in two sizes, 24x19mm (NVCWJ024Z-V1MT) and 19x16mm (NJCWL024Z-V1MT), and make posible to build lighting fixtures with adjustable color temperature from warm white 2700K to pure white 5000K.,Nichia's color tunable COB provides a smaller light emitting surface and better color mixing than other options on the market. 

Nichia Optisolis LEDs with the full spectrum of sunlight

The latest innovation in LED development is the Nichia Optisolis technology. The full-spectrum NF2W757G-F1 and NF2L757G-F1 Optisolis LEDs from world market leader Nichia are capable of generating a light spectrum that comes closest to that of the sun. 

As a result, the Optisolis family of packaged LEDs are Ultra-High CRI light sources, with almost maximum scores for all 16 of the color samples that are used in the color rendering index metric. The 5000K Nichia NF2L757G-F1 Optisolis LED can achieve a Ra of 99 out of 100 and almost maximum IES TM-30-15 levels with Rf at 98 and Rg at 99. 

The positive health effects of the uniform spectral power distribution of the SunLike LEDs from Seoul Semiconductor have been confirmed in two independent studies, by universities from Switzerland and South Korea.

The new SunLike technology brings a major improvement to the LED spectral power distribution (SPD) which now mimics the SPD of the sun within the bounds of the human visual range. The SunLike LEDs LEDs use a three-phosphor mix and a violet emitter to achieve the SPD. Seoul has said that the LEDs can be used in a variety of applications including in human-centric lighting or lighting for health and well-being where tunable lighting can be applied to improve human well-being.

 

A study published by the University of Basel in Switzerland titled “Effect of daylight LED on visual comfort, melatonin, mood, waking performance, and sleep” found that volunteers had better visual comfort, more alertness, and happier moods associated with exposure to SunLike LEDs  compared LEDs. 

The university published the research in the Journal of Lighting and Research Technology. Professor Christian Cajochen led the research team investigating what they referred to as LEDs with a daylight spectrum.

The results are based on a study of volunteers who, in two separate test sessions, were exposed to Seoul Semiconductor SunLike LEDs in one session and to conventional white LEDs at the same CCT in the other session. The volunteers exposed to the uniform spectral power distribution (SPD) of the SunLike LEDs experience better sleep patterns and reported improved visual comfort and heightened daytime alertness.

15 young male volunteers took part in the tests in Basel, spending 49 hours twice in a laboratory. During each session, the volunteers received light exposure at the same CCT and intensity levels, the only difference being the SPD of LED-based lighting products. 

Seoul Semiconductor’s SunLike Series with TRI-R technology are the world’s first natural spectrum LEDs, as they produce light that closely matches the spectrum of natural sunlight. This is made possible by using a new LED architecture, with a purple emitter in combination with a red, green, and blue (RGB) phosphor mix, unlike conventional white LED that use a blue emitter and yellow phosphor. 

This new approach has the effect of accurate rendering of colors, almost as daylight, with the added benefit of increased awareness of contrast and texture.

The high quality of the SunLike LEDs light spectrum is expressed also by the traditional color rendering index (CRI) and the new Color Fidelity Index. Therefore, SunLike LEDs have CRI 97+ and  Rf 96(TM30 Fidelity Index), values that indicate the high accuracy of reproducing the original color from 99 representative color indexes.

With the unique quality of the light spectrum, SunLike LED fixtures are perfect for lighting art, such as paintings, frescoes, mosaics, sculptures and many other exhibits. We will soon see art in many museums or historic places around the world in a new light.

Seoul Semiconductor’s SunLike Series LEDs are the world’s first natural spectrum LEDs, as they produce light that closely matches the spectrum of natural sunlight.

This achievement comes from using a new LED architecture, with a purple emitter in combination with a red, green, and blue (RGB) phosphor mix, unlike conventional white LED that use a blue emitter and yellow phosphor.  By removing the blue LED light source and replacing it with a purple light LED chip, lighting technology is fundamentally transformed. For the first time it is possible to render colors accurately with very low energy use and positive effects on health. Compared with other LED lights, the new SunLike Series does not have a blue energy peak associated with eye discomfort and poor sleep patterns.

Furthermore, an ordinary LED spectrum is very different to sunlight, whereas SunLike’s spectrum is very similar. Thus, the light sources with SunLike Series LEDs will more accurately show the color of objects, as they would appear in natural sunlight. It's natural light spectra has color rendering of CRI-97 – close to CRI-100 of sunlight, and much higher than the CRI-80 of conventional LEDs.

The SunLike packaged LED technology from Seoul is based in part on a Toshiba phosphor technology called TRI-R. By using the TRI-R, the LEDs deliver a uniform and broad spectral power distribution (SPD) that is more like sunlight than are typical phosphor-converted white LEDs.

The applications of this new LED technology, with its diminished blue light peak, similar spectral curve to sunlight, accurate rendering of colors and reduced scattered reflection and glare are many, from Human Centric lighting for our home and office to commercial and art lighting.

Human Centric lighting

‘Human-centric lighting’ describes lighting that is designed to work with the human body’s natural rhythms. It relies on the well-established fact that the human eye detects the presence of a particular wavelength of blue light in the spectrum that makes up sunlight, and uses this to judge what time of day it is. In this way, light helps regulate our sleep–wake cycles and other bodily rhythms, and has a significant impact on our mood and well-being.

Human-centric lighting harnesses this effect by adjusting its brightness and colour temperature during the day to mimic natural light. To achieve its purpose, human-centric lighting must have a spectrum that resembles that of real sunlight, with just the right level of the crucial blue wavelength that triggers the body’s response. Most solutions described as human-centric do not have a spectrum that resembles that of real sunlight, so they end up providing too much or too little blue.

Seoul Semiconductor’s SunLike Series LEDs are different, as are the first LEDs to be closely matched to real sunlight, so they have the right level of blue that trigger the desired biological stimulus.

Casambi, a pioneer in Bluetooth Low Energy (BLE) wireless lighting control, has teamed up with LED technology specialist Seoul Semiconductor to offer lighting designers precise control of LED strips, modules and luminaires that use the new SunLike technology that matches the spectrum of sunlight. For the first time, this development puts true human-centered lighting in the hands of designers.

Users can use Casambi's Bluetooth-based wireless control system and app with products that include SunLike series LEDs to precisely adjust the light level, knowing that the spectrum reflects real sunlight, a key ingredient for Human-centric lighting

Human-centric lighting describes lighting designed to work with the natural rhythms of the human body. It is based on the well-known fact that the human eye recognizes the presence of a certain wavelength of blue light in the spectrum of sunlight and derives the time of day from this. In this way, light helps to regulate our sleep-wake cycles and other physical rhythms and has a significant impact on our mood and well-being.

Human-centered lighting takes advantage of this effect by adjusting its brightness and color temperature during the day to mimic natural light.

Casambi allows control of the lights through a timer or a variety of presence/movement sensors and daylight sensors. It can control lights that change colour temperature over a very wide range, and designers have the freedom to configure dimming and create scenes or animations for the application.

Careful design of the lighting for your home will ensure that the right amount of light is gets where and when it is needed and can be switched on conveniently. Lighting should avoid over-lit areas, and give control and flexibility to create lighting effects for different situations. Well-designed lighting will be inherently easier to use and will function in an energy-efficient way.

The best approach to home lighting design is to use three levels of lighting: general lighting, task lighting and accent lighting. By combining these three levels, the recommended lighting level for each room or activity should be obtained, as below: 

Recommended lighting levels for the Home	in Lux
Living rooms general	50-150
Casual reading	150
Study	150-750
Bedroom general	50-150
Kitchen general	150
Kitchen working areas	400
Bathrooms	150-300
Halls and landings	100-150
Stairs	100-150
Dining rooms	150-450

The three levels of lighting

General lighting should ensure a sufficient minimum level of light in the room. There are plenty of LED light sources that can be used for this purpose: LED modules, strips, luminaries or spotlight. Decide on the desired illuminance level (lux). In living rooms and bedrooms in particular, give a certain degree of flexibility (through control settings/dimmers) so that occupants can raise or lower the general lighting around the set level. Design for the upper end of the Lux ranges in homes with elderly occupants, which generally appreciate a higher level of general lighting. A minimum level of general lighting is required for safe movement in the home, especially on the stairs, but sufficient general LED lighting is considered important for general well-being.

Workplace lighting is needed for certain activities at home, such as reading, preparing food and working from home. LED lamps must be carefully selected, correctly positioned and controlled. Recommended are LED spot lights and high flux LED modules. Lamps or sockets are needed in the right places to ensure flexibility in the availability of work and accent lighting. Depending on the task, LED workplace lighting may be required at different levels. The colour rendering of the light is also very important for some activities and we recommend LED lights with CRI 95 or more.

Accent lighting contributes to the ambiance of a house and is usually done with LED spots and strips. As with workplace lighting, LED luminaires (or sockets) are placed in the right places to emphasise architectural features, furniture and ornaments. Accent lighting is a more personal matter, and depending on the circumstances, spotlighting or floodlighting can be useful.

For each of these levels of lighting, controls can provide a range of lighting options. So in an living room there could be separate controlled circuits for:

• general lighting 
• task lighting (typically positioned under the wall units) 
• accent lighting 

Similar control patterns can be considered in other rooms, with dimmers providing a different lighting atmosphere in salons, dining rooms and bedrooms. Advanced controls, sometimes controlled by a mobile phone or a tablet app, that allow remote adjustment of the amount of light and its color are increasingly popular. Lighting is establishing itself as a lifestyle statement and houses with new and innovative lighting systems are perceived as a marketing advantage.

Lighting of each room in detail:

Living rooms

The new Vitasolis™ technology from Nichia are LED light sources with spectrum meant to stimulate activity. 

 This development in based on recent research that has revealed in detail the relationship between light and human behavior. Humans can recognize the brightness and color of light while human circadian rhythms can be affected by different wavelengths, especially the blue-green area. For example, lighting has an effect on the level of activity throughout the day, including wake up in the morning, daytime activities, and nighttime sleep aids.

Vitasolis has a very natural white light and its spectrum contains more energy in the blue-green region, which helps control the human circadian rhythm. The spectral distribution of Vitasolis clearly illuminates the object while maintaining high light efficiency.