Imagine two white lights of different tones placed side by side. Won’t you find such inconsistent light colors odd and visually uncomfortable? To avoid such failures in lighting, consideration of SDCM is very important. It measures the color consistency of light and ensures uniform and flawless light output.
Get ready to explore all about SDCM and choose the right LED strip lights for your project.
What Is SDCM?
The term SDCM stands for ‘Standard Deviation Color Matching.’ It measures the color and determines how closely one color matches or doesn’t match the other. It uses the same principle of the MacAdam ellipse for measuring the color consistency of the light source.
The color of the two lights will never be exactly the same. But you will always not be able to detect this difference. There are color tolerance levels at which human eyes can’t detect these differences. You can detect the color derivation of the lights through the MacAdam ellipse.
Based on the distance from the targeted color, the ellipse is divided into several SDCM steps. For lower steps, no or less color difference is noticed. For higher steps, your bare eyes can identify color differences between light sources.
| MacAdam ellipse (SDCM) | Visibility |
| 1 SDCM | Almost no visible deviations |
| 2 SDCM | Deviations are visible only with instruments |
| 3 SDCM | Few deviations visible with the human eye |
| 4 SDCM | Visible deviations |
| 5 SDCM | Strongly visible deviation |
Understanding SDCM With Example
Have you ever purchased two lights of the same CCT, but their color seems different when you turn them on? There’s nothing to be surprised about. This can occur due to a difference in SDCM. Let me make it clearer with an example.
Suppose you have two fixtures of 3000K CCT. However, one is for SDCM 2, while the other is for SDCM 5. The one with 2 SDCM will show an identical color of 3000K, which is warm white. At the same time, higher SDCM, like 5 or above, will have differences in color consistency and saturation. Therefore, for differences in SDCM, you can find 3000K light appears greenish or reddish.
Practical Application Of SDCM
When purchasing any light, the common metrics that we all match are CCT and CRI. But the twist is that only these two facts can’t ensure the color consistency of lights. As I discussed in the above example, two fixtures of the same CCT can end up appearing different due to SDCM values. Therefore, to ensure color consistency, you have no option to skip SDCM.
Usually, indoor spaces or applications where accurate color maintenance is essential require less SDCM. This ensures color consistency and the lighting of your space is compact. In general, the 2 top 3 SDCMs are preferable for indoor lighting. However, in outdoor spaces, fixtures with more color derivation are okay. You can go for 5 SDCM or above based on lighting requirements.
| Application | Suggested SDCM |
| Art Galleries and Museums | 1-2 SDCM |
| Healthcare Facilities | 1 – 2 SDCM |
| Residential Spaces | 1 – 3 SDCM |
| Office Spaces | 3 – 4 SDCM |
| Manufacturing and Industrial | 4 – 5 SDCM |
| Outdoor Lighting | 5 or higher SDCM |
Importance of SDCM In LED Strips
Consistency & Uniformity of Color
Low SDCM is essential to maintain color consistency. This ensures the light sources look identical. Therefore, while you purchase lighting for museums, art galleries, or similar applications with high color consistency requirements, look for low SDCM fixtures.
Visual Comfort
Light with high SDCM appears very different when placed side by side. Such lighting naturally creates an idea of faulty light setting to any visitor’s mind. This kind of inconsistent lighting creates glaring issues and makes you uncomfortable. So, it is important to use low SDCM lights for smooth and uniform lighting.
Maintaining the Quality of LED Chip
The manufacturer uses SDCM as a standard to maintain the color consistency of the light. As a result, all the chips given off are the same color. So, the lighting of the LED strips looks flawless due to color consistency. Thus, consideration of SDCM value improves the quality of the final product.
Long-Term Performance
The color of the fixture gradually shifts with time. So, with high SDCM lights, the variation of light will be more prominent. In contrast, if you use a low SDCM light, it will minimize the color variation issues. You can thus use the fixture for a long time without requiring replacement.
Guides In Purchasing the Right LED Strips
You must strictly follow color consistency in applications like museums, theaters, art galleries, and commercial lighting. In this case, SDCM will guide you in picking the right LED strips. For lighting areas where visual appearance is crucial, use low SDCM lights. 1 to 3 SDCM will work great. Again, SDCM is not a major issue in outdoor lighting. You can go for higher SDCM ratings.
What Factors Affect The SDCM of LED Strip Lights?
Use Of Low-Quality Material
Gradually, the color shift of light with aging is a normal phenomenon. However, the use of low-quality material causes early color shifts in LED chips. As a result, the SDCM values get higher quickly than the normal level, and the light color remains constant no more. Again, the thermal capacity also reduces the use of poor materials. This overheats the lights and encourages color shift due to changes in SDCM.
Changes In Drive Current
The flow of current influences the color output of light. What actually happens is that when the current flow inside the LED chip increases, the temperature of the diode also increases. This changes the emission of color spectrums, which causes color shifts. And this is why the SDCM also gets higher. Besides, frequent changes in drive current affect the lifespan of the light.
Wrong Installation
Operating temperature has a greater impact on SDCM. When there is no sufficient heat dispersion facility in LED strips, they get overheated. Due to the rise in temperature, the CCT also increased. Thus, the warmer hue of the lights tends to give a bluish tone. This rise in color temperature brings changes in SDCM.
Use Of Diffusers
You often use a diffuser with an LED strip. These act as a covering of the LED light. That is, the light rays pass through the diffusers before spreading to the surroundings. This causes color derivation and SDCM changes in the final output of light. So, the LED strip you bought
How To Reduce The Color Tolerance Distance? Lowering SDCM
You can reduce the SDCM value and achieve targeted light color following the below three methods:
1. Color Mixing Method
The color mixing method is an effective way to lower the SDCM and match the targeted color. Here, you need to select two or multiple LED chips from the factory’s color separation cake or color bins. Then, mix them in equal or unequal proportion to achieve the SDCM step closer to the targeted light source.
2. Adjust the Bin Center Method
The white LEDs often use phosphorus coating. By adjusting the ratio of phosphorus, you can take the central points in opposite directions. Thus, the SDCM will lower and go closer to the targeted light color.
3. Hot Bins Method
In the hot bins method, you have to increase the working junction temperature while color separation. The temperature should be equal to the operating temperature of the LEDs. This way, by increasing the working junction temperature, the SDCM will reduce a lot. For more information, you can check What Is LED Binning?
What Is The Color Temperature?
Color temperature describes the color of any light source. It compares the color of a black body radiator to the light source. When a black body is heated, it changes its color with the rise in temperature. The color sequences follow as follows:
| Deep Red → Light Red → Orange → White → Blue |
The temperature at which the color of the blackbody matches the color of the light source is the light’s color temperature. For example- the blackbody at 3000K appears warm yellowish-white. Similarly, the light source of color temperature 3000K also appears the same.
In traditional lights like incandescent, the difference in color temperature is huge, about 150K. So you can visually detect the color shifts. However, in LED lights, the variation in color temperature can be as small as just 15K.
Correlated color temperature (CCT) measures the tone of white lights in Kelvin rating. For higher CCT, the lights appear cool, and for lower CCT, the lights get warmer.
| CCT | Light Color |
| 2700K | Warm white |
| 3000K | Soft white |
| 3500K | Neutral white |
| 4000K | Daylight white |
| 5000K and above | Crystal white light |
However, with a definite CCT, you can still find visible differences in light color. For example- CCT 3000K rated bulbs can appear greenish, warm white, or reddish. Even after these color differences, they are all known as 3000K bulbs. Therefore, you can say that CCT is basically a range of color temperature within which color temperature value fluctuates.
So, how do you identify the accurate light color? To detect the exact color of the light, you need to consider SDCM.
What’s The Relationship Between SDCM and CCT?
The changes in CCT are related to the shift of SDCM steps. This is why two light sources of the same CCT may appear to be different in color.
Let me explain the relation between CCT and SDCM with an example. Suppose you bought two lights with a standard 3000K CCT rating. However, due to differences in SDCM, the two lights may appear different.
- 1st Light With Low SDCM: <5
See in the diagram; the SDCM rating for the first light is closer to 3 SDCM and is less than 5. Here, the exact CCT is rated as 3061, and it appears to be warm white in color.
- 2nd Light With High SDCM: >7
The SDCM of the second light is far away from the targeted point. It goes above 7SDCM steps and appears greenish in color. The CCT rating for this is 3078K.
Even for just 17K variation in CCT, two lights have very different color outputs due to greater differences in SDCM.
What Are the Advantages of High CRI and Low SDCM?
CRI is another metric related to light color. It determines the color accuracy of an object under artificial lighting. It is graded from 0 to 100. High CRI means the color of an object under the fixture is closer to the natural lighting.
In contrast, SDCM determines the color shift of a light compared to another targeted light source. Low SDCM means less color shift and similar color output. Therefore, a fixture with high CRI and low SDCM brings out high-quality lighting. The benefits you get using these lights:
- Higher color accuracy
- Color consistency and uniform lighting
- No glaring issues reducing eye strain
- Comfortable visual
Besides, high CRI and low SDCM lights are essential for commercial lighting. In retail stores, high CRI lights show accurate product colors to customers. Again, you will get a comforting and uniform light setting for shopping under low SDCM lights.
SDCM & Chromatic Aberration: Differences & Relation
SDCM compares the differences between the X and Y values of a light and the X and Y values of a standard light source. For smaller differences, the SDCM is low, indicating a closer match to the targeted light color.
In contrast, chromatic aberration refers to the difference in light color. It measures the difference between the values of X and Y coordinates of two light colors. The smaller the gap, the lower the chromatic aberration. That is, the difference in color is minimal, and so they look alike.
Difference Between SDCM & Chromatic Aberration
The two terms, chromatic aberration and SDCM, are different. Let’s consider an example to understand their differences. Here, we take four light sources – A, B, C, and D as samples. Their X and Y coordinate value and SDCM are as follows:
| Example For Explanation | ||
| Light Source | Value Of X | Value Of Y |
| A | 0.3856 | 0.3876 |
| B | 0.3757 | 0.3728 |
| C | 0.3801 | 0.3860 |
| D | 0.3826 | 0.3917 |
Using the X and Y values, let’s now find the SDCM and chromatic aberration of these light sources:
SDCM of Light Source A, B, C, and D
Placing the values in a chromatic graph, we can find their SDCM steps as follows:
Fig: SDCM steps for light sources A, B, C, and D.
| Light source | SDCM |
| A | 3 |
| B | 3 |
| C | 3 |
| D | 5 |
Chromatic aberration for the light sources:
- Chromatic aberration of A & B
Subtracting the X and Y value of B light source from A,
X-axis = (0.3856 – 0.3757) = +0.0099
Y-axis = (0.3876 – 0.3728) = +0.0148
So, the chromatic aberration of A-B is (X=+0.0099, Y=+0.0148)
- Chromatic aberration of A & D
Subtracting the X and Y value of the D light source from A,
X-axis = (0.3856 -0.3826) = +0.0030
Y-axis = (0.3876 -0.3917) = -0.0041
So, the chromatic aberration of A-D is (X=+0.0030, Y=-0.0041)
Therefore, it is seen that the chromatic aberration difference between A & B is greater than A & D. This means the difference between A and B is more prominent and visible than that of A and D.
Again, the SDCM of A and B are both 3, so they have color consistency. Meanwhile, in A and D light sources, the SDCM of D is two steps higher than that of A. This means that A and D don’t maintain color constancy. So, comparing SDCM and chromatic aberration, you can come to the conclusion that these two terms are totally different. But how are they related?
Relationship Between SDCM & Chromatic Aberration
You can understand the relationship between SDCM and chromatic aberration with McAdam’s experiment. The pictures below show the different SDCM steps in the MacAdams ellipse at 3000K color temperature:
Here, you can see that for the 2-step MacAdam ellipse, the chromatic aberration or color difference is barely observed. However, for 3 SDCM, you can notice the color abbreviation slightly. Likewise, the color difference becomes more prominent in 5 and 7.
Therefore, you can find a relationship between these two terms, as when SDCM increases, the chromatic aberration also increases. Thus, the difference between the two light sources is more visible.
What is Duv?
Duv stands for ‘Delta UV.’ It is another matric for LED lights that indicates the shift of light color from pure white in a chromaticity diagram. This refers to whether the white light has a greenish or pinkish tint.
The value of Duv can be positive or negative. When the chromaticity point of the light source is located above the Planckian locus, it’s a positive Duv. Again, when the point is located below the Planckian locus, it is negative Duv.
| Duv | Value | Tint & Tone |
| Positive Duv | Above zero | Greenish tint with a cool tone |
| Negative Duv | Below zero | Pinkish tint with a warm tone |
When the Duv value is above zero, it is called positive Duv. The light color appears cool and gives a greenish tone. Again, when the Duv goes below zero, the light seems to have a pinkish tint and is warm.
So, for accuracy, you should always prefer a zero Duv. This ensures no color deviation from the ideal CCT appearance.
Same CCT & SDCM with Different Duv
Lights with the same CCT & SDCM may look different due to differences in Duv value. For instance, let’s take two LED lights with 4000K CCT and SDCM 1. Suppose one has a positive Duv of +0.003 while the other has a negative Duv of -0.003.
Now, in spite of having the same CCT and SDCM, the light with positive Duv will appear greenish. Meanwhile, the light with negative Duv will appear warmer and pinkish. So, considering Duv value is essential to maintain light consistency.
Note: For balanced and accurate CCT, always opt for zero Duv and low SDCM.
SDCM Standard In LED Industry
The coordinate values of the standard color temperature SDCM center corresponding to the North American ANSI standard and the European Union IEC standard are summarized as follows:
IEC 60081 Document Download: BS-EN-60081-1998 IEC-60081-1997
| Color Temperature Range | ANSI C78.377 | IEC 60081 | ||||
| X | Y | CCT | X | Y | CCT | |
| 2700K | 0.4578 | 0.4101 | 2722K | 0.4630 | 0.4200 | 2726K |
| 3000K | 0.4338 | 0.4030 | 3041K | 0.4400 | 0.4030 | 2937K |
| 3500K | 0.4073 | 0.3917 | 3460K | 0.4090 | 0.3940 | 3443K |
| 4000K | 0.3818 | 0.3797 | 3985K | 0.3800 | 0.3800 | 4035K |
| 5000K | 0.3447 | 0.3553 | 5024K | 0.3460 | 0.3590 | 4988K |
| 6000K | 0.3123 | 0.3282 | 6531K | 0.3130 | 0.3370 | 6430K |
1. North American Energy Star Standard
The North American Energy Star Standard is popularly known as Energy Star ANSI C78.377. The color tolerance level, according to this standard, is ≤ 7 SDCM.
| Color Temperature Range | ANSI C78.377 | |||||
| 3 Steps | Distance | 5 Steps | Distance | 7 Steps | Distance | |
| 2700K | 2670-2780K | 110 | 2630–2830K | 200 | 2580–2880K | 300 |
| 3000K | 2970–3120K | 150 | 2920–3170K | 250 | 2870–3220K | 350 |
| 3500K | 3360–3560K | 200 | 3300–3650K | 350 | 3230–3730K | 500 |
| 4000K | 3860–4110K | 250 | 3770–4220K | 450 | 3680–4330K | 650 |
| 5000K | 4860–5210K | 350 | 4750–5300K | 550 | 4650–5450K | 900 |
| 6500K | 6300–6800K | 500 | 6150–6950K | 800 | 6050–7150K | 1100 |
2. EU IEC Standard
The fixture should maintain the EU IEC 60081:1997 standard for selling lights in Europe. According to this standard, the color tolerance is ≤ 6 SDCM.
| Color Temperature Range | IEC 60081 | |||||
| 3 Steps | Distance | 5 Steps | Distance | 7 Steps | Distance | |
| 2700K | 2680-2790K | 110 | 2640–2840K | 200 | 2590–2890K | 300 |
| 3000K | 2865–3015K | 150 | 2820–3070K | 250 | 2770–3120K | 350 |
| 3500K | 3350–3550K | 200 | 3280–3630K | 350 | 3210–3710K | 500 |
| 4000K | 3910–4160K | 250 | 3820–4270K | 450 | 3740–4390K | 650 |
| 5000K | 4810–5160K | 350 | 4720–5270K | 550 | 4620–5420K | 900 |
| 6500K | 6200–6700K | 500 | 6100–6900K | 800 | 5950–7050K | 1100 |
3. Chinese GB standard
The Chinese standard GB 10682-2002 is designed for fluorescent light. According to this standard, the color tolerance is ≤ 5 SDCM. This can also be used for LED lights.
North American Energy Star Standard VS. EU IEC Standard
| Criteria | EU IEC Standard | North American Energy Star Standard |
| 2700K Color Temperature | Allows significant deviation from the black body curve, often resulting in yellow or greenish tones. | Maintains closer adherence to the black body curve, providing more natural, accurate warm light. |
| 3000K Color Temperature | Tolerance range (2865K–3015K) with a center point at 2900K, leading to a warmer-than-expected light output. | Delivers a more consistent 3000K, matching customer expectations for true white light. |
| 6500K Color Temperature | Permits too much deviation from the black body curve, causing unnatural lighting effects, especially in commercial or industrial settings. | Provides more accurate daylight-like lighting, ideal for environments requiring precise illumination. |
The North American Energy Star standard offers better color accuracy, with less deviation from the black body curve. This results in more consistent, natural lighting across key color temperatures (2700K, 3000K, 6500K), meeting customer expectations more reliably.
Impact of International Standard on SDCM
Difference in CCT Range
From the above charts of ANSI and IEC, you can see differences in their CCT ranges for different SDCM steps. The major differences are visible for 2700K, 3000K, and 6500K. Therefore, when considering color tolerance level, make sure to consider which standard you are following.
More Accurate Color Selection
When a customer refers to the CCT with the SDCM step, you get guidance to provide them with an accurate light color. For example, a customer needs a light of 3000K-3300K with SDCM less than 5 as per European standards.
Now, as per the IEC 60081 standard, 3000K-3300K for 5-step SDCM falls under two ranges. For 3000K, it is (2820-3070K). Here, you will get a CCT option of only 70K (3000K-3070K). Again, for 3500K, the 5-step range is 3280-3630K. Here, the CCT variation option is only 20K (3280-3300K). So, the light you give to the customer must fall under this range.
Machine Difference Causing SDCM Shift Problem
Even after having the same SDCM, the light color of the two manufacturers may appear different. This may occur due to differences in machine standards, which shift the central point. As a result, the color may appear different even with the same SDCM.
How to Test SDCM LED Strip?- For SMD5050 LED Strip
SDCM of LED strip lights is tested using a big integrating sphere machine. It is connected to a spectrometer that determines the color consistency of the LED chip. For this test, I am using a SMD5050 LED strip.
| Test Machine | Big integrating sphere machineSpectrometer machine |
| Test LED | SMD5050 LED Strip Light in a warm white color |
| Light Source Data | CCT: 3000K |
| Flux | 600lm |
| Length | 50cm |
| LED Quantity | 30LEDs |
You can see the SDCM value of this light in the upper right corner of the test report, 1.5SDCM. This is very close to the standard value. For more information, you can check How to Read the Integrating Sphere Test Report.
Challenges in Measuring And Controlling SDCM For LED Strip
To maintain low SDCM, you need to go through a strict manufacturing process and quality assurance. This requires specialized equipment, a reliable manufacturing team, and advanced technologies. All these increase the production cost of the LED strip.
FAQs
Wrapping Up
SDCM is an important matrix to ensure color consistency between light fixtures. However, you should always consider applying to pick the right SDCM for your lights. Always use low SDCM lights indoors. This will ensure uniform and consistent lighting all over the room. Besides, buy lights from reputed brands that test SDCM and strictly maintain the value.
