This question still comes from an article by iN yesterday titled "2 Meters 11! Accidentally made one of the world's largest "screen hanging lights", which has two replies:
So we can start today's content with the color rendering index (CRI). The average person will be fooled by many merchants, saying that the color rendering index is high for the eye protection of lamps and lanterns, and there are also many merchants who will flaunt their own lamp color rendering index Ra greater than 95... As soon as the value is reached, many ordinary people will be in a daze, completely do not understand ah... Moreover, many marketing numbers or manufacturers will also give you something like this:
For example, in the figure above, the only thing iN can agree with is that the color rendering index is an important criterion for measuring the quality of light sources. The rest is hehe, but even "an important standard" is not enough to be a "crucial standard". There is a big difference between the two.
To figure this out, let's first look at what the color rendering index is:
The color rendering index refers to "a measurement method for color recognition in terms of a light source compared to a standard reference light source" For this reason, the International Institute of Illumination has introduced a standard measurement method called CRI (color rendering index color blend index). Literally, CRI is a tool for studying how light smudges the color of an object.
The Ra index we are talking about is the average of the color deviation of R1-R8 in the standard reference light source above, and the average of the color deviation in the larger range of the substantial R1-R15 that Re rarely mentions by the manufacturer.
Returning to our traditional saying "no color under the lamp", we will find that our ancestors have long ago discovered that light will cause smudging of the color of the object's natural color, causing some colors to be too light or oversaturated. The Chinese experience is philosophical, but in the Western Illuminating Society, it began to conduct quantitative research on this aspect.
This incident originated in the culture of Europe and the United States, where Europeans and Americans found it difficult to find cars of their own color in the parking lot at night many years ago. The main problem was the high-pressure sodium lamp used in the public lighting of the Parking Lot in Europe and the United States
It is a luminous luminaire with high luminous efficiency, bright and power-saving, and was widely used in public lighting after World War II. But the disadvantage of sodium lamps is that the spectrum is very narrow, only concentrated in a narrow category of 589nm-589.6 nanometers, which is what we call dim light.
In this light, the object also loses its color characteristics.
To this end, European and American countries have put forward requirements when improving public lighting, requiring that the lighting system in the public environment can show the original color of the object as much as possible. This is where CRI comes from.
Seeing this, everyone will think that the CRI is very good, it can ensure that the lamp gives us the correct color. That's how much I think about it. Let's take a look at the spectral control chart:
Sunlight, incandescent lamps, high-pressure sodium lamps, fluorescent lamps, LED cold white light, LED warm white light each have their own different spectrum. Here back according to the first part of the article, iN added a word "standard reference light source", if the surface sunlight as the standard light source to see the 6500K irradiation environment as the standard, all other lights are difficult to think of sunlight with Ra100 color rendering index. If you look at the color temperature standard of 3000K, you will find that the color rendering index of incandescent lamps is Ra100! The reason is that the standard light source with a color temperature of 3000K is an incandescent lamp. So then again, do you think that the colors you see under incandescent lights in the early years are the same as the colors you see in the sunshine on a sunny day? So when we play with film, we will distinguish between light films and daylight films. Of course, today's young people rarely play with film cameras, and more people will only adjust the white balance even if they play with cameras.
The color is simply unreliable under different lights, not to mention the difference in color temperature brought about by the choice of standard reference light source, which will also lead to inconsistencies in the color of the light itself.
Because of this, in fact, this CRI standard has not been a mainstream standard in foreign countries for many years. Although it has not been officially abolished, most foreign lighting brands do not label the CRI Ra index of their own lamps. Take GM Philips, a company that has been playing with lighting since the 18th century.
Due to the problem of light color, the U.S. Department of Energy still took the trouble to promote CRI, and in 2008 launched the L Award to promote the development of high-color LED lamps, and in 2011 Philips was the first to win the L Award.
If placed in China, this kind of award is a publicity gimmick, but Philips still does not advertise the CRI index. If we take apart their award-winning A19 bulbs we see beads of different color temperatures to mix to get the final light color
This technology has been brought all the way to high-end luminaires such as Philips such as Hue. Let's look at the dismantling of Hue and the dismantling of a light bulb from China, which can also see the difference
iN's own lamps and lanterns are actually this effect:
Three LED beads are used to emit light of different color temperatures, and the effect of white light is achieved by calculation and mixing. As for how much the "color rendering index" is really not marked, iN itself feels that there is no need to care.
As for the light strip mentioned by the previous fans, there are foreign forums testing, and the different color temperatures in the white light mode will be between 85-91. If it is for domestic manufacturers, it will be directly marked as RA>90.
But in iN's own understanding, the Ra index is currently an IQ tax. Therefore, CRI is an important indicator, but just looking at this indicator does not reflect the lighting situation, and it cannot be considered that high Ra value lamps are eye protection lamps, and there is no direct connection between the two.
At the same time, to say a point: CRI is not not used now, European and American manufacturers more use of color gamut index (GAI), color quality level (CQS) and other indicators to indicate the color rendering of lamps. But this is still not the "crucial standard" for luminaires.