Color consistency represents a light quality index for led light fittings. The indicator called correlated color temperature, describes white light as neutral, warm (reddish), or cool (bluish). Even when the CCT value is same, there is variation that can be easily discerned. LED lighting manufacturers aim to ensure color consistency by developing methods to strictly control color variations.
For this reason, LED manufacturers develop various proprietary binning optimization processes in order to achieve the best possible color consistency. Through high performance LED optimization processes, the color variations are tightly controlled. Some LED manufactures employ advanced bin selection formulas that exceed chromaticity industry standards in order to guarantee consistency and uniformity of color temperature and hue.
CCT – Correlated Color Temperature
The temperature in CCT refers to the black-body radiation. This is actually the emitted light by a solid object heated to the point of incandescence. The CCT value is expressed in degrees Kelvin, which is absolute temperature’s standard measurement. The emitted light by a black body as it gets hotter progresses through a particular sequence of colors that follows a curve within a color space. Starting from red, the light passes to orange, yellow, white and blue.
For example, The color of the emitted light by an incandescent lamp is around 2700K. This value is toward the reddish or warm scale’s end. Visible light’s spectral analysis allows defining color temperatures for white light sources that are non-incandescent, such as LED lighting and fluorescent tubes. Even if the LED provides same light color as a 2700 K heated filament, it has an actual temperature of around 80C.
There are several standards defining the various light sources’ chromaticity. For example, for LED sources there are 8 nominal CCTs that range from 6500 K (daylight white) to 2700 K (warm white). Among these CCTs, six correspond to the compact fluorescent lamps’ chromaticity specifications, in order to ensure some consistency across various types of light sources. Another two additional CCTs have been defined in order to cover the gaps not accounted for by the CFL chromaticity standard along the curve, since LEDs can produce any variation of the color temperature within the range.
Allowable CCT Variations
An allowable range of tolerance or variation corresponds to each nominal CCT, both perpendicular to the curve and along the curve. Variations along the curve cause the light source to look more bluish or reddish, while those variations that are above and below the black-body curve cause the light to look more pinkish or greenish. These variations along the black body curve are measured in degrees Kelvin, while variations perpendicular to the curve are notated as Duv.
Within each color temperature’s color space, the allowable CCT variations both perpendicular and along to the curve define a quadrangle. The Duv and CCT ranges for the temperature of each color determine each quadrangle’s size.
For instance, the nominal CCT of 3000 K’s quadrangle has a tolerated variance of plus or minus 175 K, being centered on 3045 K. The 3000 K quadrangle covers along the black- body curve from 2870 K to 3220 K. In practice, even if the measured Duv and CCT of LEDs can vary considerably, the values are still considered to have a nominal 3000 K CCT.
Achieving Consistent Color
LEDs vary in lumen, CCT and voltage during the production process. Because these differences can be significant, LEDs are delivered to the market in bins. This binning process makes it possible selecting LEDs that conform to the stated specifications. For example, binning allows selecting LEDs for car lights that meet the American standard when it comes to the specific color required.
Lighting fixture manufacturers develop various methods of selecting LEDs bins in a way that allows minimizing color differences that might be visible from production run to production run or from fixture to fixture.
Some LEDs Manufacturers offer 16 bins for a 2700 K nominal CCT. However, there will always be a certain range of variation in Duv and degrees K from bin to bin. In order to ensure color consistency, some LED lighting manufacturers aim to exceed the standard by adopting standards for LED packaging. For example, Myledy has designed a sorting mathematical model, called Ledybin. This mathematical model guarantees color uniformity across production runs for all led strip lights.
Rather than following the 7-step ellipse of the ANSI standard, LED fixtures’ hue tolerances and Ledybins CCT fall within a 4-step MacAdam ellipse. Ledybin will use LEDs from bins that are as close as possible to the curve within a 4-step ellipse in order to ensure that the color variations are barely noticeable.
Within a 4-step MacAdam ellipse, there are 4 bins. However, for manufacturing run to manufacturing run it is used only one bin, so the consistency is always within 2 SDCM per batch and per reel.
Proprietary Ledybin algorithms are used in order to ensure led strip lights color consistency from batch to batch and reel to reel. It is particularly important to ensuring reliable color consistency over time for expansion and multi-site installations, for phased installations where fixtures are purchased and installed at different times, and in case of fixture failure for color-matching replacement fixtures.
What CCT can we offer?
Myledy can offer white color temperature of led strip lights from 2100K to 6500K, welcome to check our strip range for detail.