Whether you are an artist and a pigment palette experts or not, Human's eyes are sensitive to the quality of light and the color. In your experience of life, you can find that a red shirt in the sunlight is much different from the under a fluorescent light. So we will ask why the same color (the same dress, the same color ornament) looks so different in different light (different from: unsaturated, color shift, dim, untrue, etc. )
Normally, the standard light source is the sun. Compare with the sun, Color presentation depends on the restore quality of light. Now there are several ways to test the quality of light source:
- Color Rendering Index (CRI)
- IES TM-30-15
- Color Quality Scale (CQS)
- What is the Color Temperature (CCT) ?
We need to notice the different of color presentation and color temperature. A brief summary of color temperature as below:
In the lighting industry, color temperature (CCT) refers to the color appearance of the emitted light. Not all the white lighting is the same. As you know, They seemly emit different color of white when some metal are heated to specific temperature (K), such as 3000K for warm white, 4500K for natural white or 6500K cool white.
For example, White lighting can have some warmer color. It looks close to yellow, amber, orange or even slightly bluish white, very bright. There is a kind of natural white between the warm white and cool white looking like the sunlight close to the noon.
We all know the color temperature of sun at noon is cooler (bluish) than the sun at sunset. This is correlation of color temperature.
Color Rendering Index, normally we call CRI for short, it used to judge the lamp light the goods how close it is when compared with sunlight. CRI area could be from 0-100, the higher value, then more close to its color under sunlight.
If one lamp CRI is 100, that means there is no difference between sunlight light the goods. If CRI value is 75, that means its light effect , its color only close to 75%.of sunlight lighting effect. Of course, different lamp CRI comparison, best to use same CCT.
CRI will be helpful for us to judge the lamp light if it is good or not to show the goods color by eye checking, how close it is.
When we talk about accurate color, it usually mean the color we can see under sunlight ( used sunlight as the standard), if the lighting with CRI>90, means this lighting with excellent ability to show the goods color, while CRI between 80-90 is good option already.
Pay attention, CRI 100 doesn’t mean that it is a prefect lighting and color rendering. CRI value is a close value between the observation light and reference light ( the sun ).
Learning from other related issues, NIST ( National Institute of Standards and Technology ) propose a new standard metric called CQS ( Color Quality Scale ) in order to deal with the problems that the disadvantage from standard color selecting and applied to a mathematical methods of color synthesis results; Meanwhile, it can keep the advantage of CRI and point out the direct relationship with the real world when it applies to test for standard color chips. CQS is tried to use lots of color samples to solve the major problem of CRI, such as IES TM-30-15 use the 15 color samples to instead of original 8 color samples. Choosing these saturated color of balanced distribution in the visible spectrum.
Color Rendering Index(CRI)
How faithfully the light source can reveal colors like the sun, using 8 color samples.
Fidelity Index (TM-30-15)
How faithfully the light source can reveal colors like the sun, using 99 color samples.
Gamut Index (TM-30-15)
Indicates the change in saturation of colors (That is how intense the colors are).
Color vector Graphic (TM-30-15)
Which colors are saturated or unsaturated and whether there is a hue shift in any of the 16 color bins.
CQS - Color Quality Scale
An alternative to the unsaturated CRI measurement colors. There are 15 highly saturated colors that are used to compare chromatic discrimination, human preference, and color rendering.
Fidelity Index (Rf)
Which is a similar measurement to the CRI (Ra) standard that measures color rendering based on comparison to a color palette of 99 colors (CRI only had 9 colors)
Gamut Index (Rg)
Which measures the average gamut shift (hue/saturation) of the light source. A graphical representation of Rg to visually represent which colors are washed out or more vivid due to the light source.
Test sample #9 is a strong red. A low value of R9 means that the light source does not render strong reds the same as the reference illuminant.
Why is this important?
CRI can be found on lamp cue sheets today and is not going away. The IES is still in feedback and will most possibly make some forms of adjustment to TM30 before it replaces CRI.
TM30 will most possibly start to be used in some places like specifiers, retail shops ,antique shop, jewelry store etc, where color rendering is a prime concern.
Relative to TM30, CRI is gamble, because it only compares 9 colors to the 99 colors that TM30 compares. So if you engineer your product’s output to those 9 colors, you can increase your score without actually improving the quality of the light source.
1.The black circle represents the reference light (the sun) and the red shape is representative of the test light.
2. The black circle is made up of the 16 hue bins (colors put into categories) of the reference light.
3. Any red line inside of the black circle means that those hues are desaturated by the observed light when compared to the reference light.
4. Any of the red line outside of the black circle means that those hues are oversaturated by the observed light when compared to the reference light.
5. When the red line overlaps the black line, the hues presented are the same for both lights being compared.
QUICK OVERVIEW OF COLOR VECTOR GRAPHICS:
- Outward shift represents more saturated colors
-Inward shift represents desaturated colors
- Sideways shifts (the whole red shape shifts) mean a hue shift
- Lastly, no shift means that the colors are not distorted
LED Lights are one of the best tools for designing, no matter for interior designer, photographer or artist who work with colors.
Deno owns high light output LED Strip which achieve 135lm/W; These strips also with high CRI(93) and high Rf and Rg. The strips with high CRI & high Rf & Rg can help photographer to get bright and natural looking for the studio, and display goods in better and more authentic statement, Deno’s Strip can be applicated in any of commercial or residential lighting projects.
To supporting our customers better, Deno Lighting also offer custom service. Providing the best LED Lighting and professional service is what Deno always insist on.
CQS(Color Quality Scale) is another method to determine and analyze lighting quality, Developed by?NIST, it was also created for the need to find an alternative to the unsaturated CRI colors. there are 15 highly saturated colors that are used to compare chromatic discrimination, human preference, and color rendering (the method evaluates 15 colors to more accurately span the range of normal object colors)?Source.