Technical Reference

Color accuracy in lighting: artificial and natural lighting

In our various discussions about color rendering and lighting quality, we oftentimes reference color accuracy. But what does it mean to be "accurate" and why do we care? We discuss this question in detail below.   The transition from natural to artificial lighting Ou...Read More

Luminosity curve data (CSV/Excel format)

You can find the luminosity curve data in text format from the following link here....Read More

How to open MYD and HAAS files for lighting photometric tests

If you've worked around LEDs and LED lights for awhile, you've undoubtedly come across lighting photometric reports. If you have any files that end in .MYD or .HAAS, you will need special software to open these files. What is an MYD file? How do I open an MYD file? MYD f...Read More

Black body and reconstituted daylight locus coordinates by CCT (CSV/Excel format)

Below you will find the coordinates in both CIE 1931 xy and CIE 1976 u'v' for both the black body locus and daylight locus, listed by 10K and 1K CCT increments. Alternatively, an interactive calculator is also available here. The d...Read More

What is the difference between the black body and the reconstituted daylight spectrum?

The black body spectrum is a spectral plot of a "theoretical object" that emits radiation (black body radiator) at a particular temperature. The sun is often mentioned as an object that comes close to a true black body radiator, and this makes it relatively straightforward to calculate the solar spectrum based on Planck's l...Read More

How to calculate the daylight spectrum (D illuminant)

Measuring and characterizing the daylight spectrum can be challenging due to the fact that many factors affect it, including time of day, season and weather. That being said, it is oftentimes necessary to standardize the daylight spectrum and this is what the D illuminant attempts to do. The D illuminant can ...Read More

CRI/Ra test color samples (TCS)

The Color Rendering Index (CRI) is a widely used metric to describe color accuracy and fidelity. It is calculated as an average score on 8 color samples (called TCS or test color samples), with an additional 7 supplemental color samples for the extended CRI (e) metric. Each of these scores is called Ri...Read More

What is CRI R9 and why is it important?

CRI R9 is one of the test color samples (TCS) used in the calculation of CRI. Because CRI is an averaged, single number, it can fail to capture the detail of how particular colors are rendered. To address this shortcoming, a closer look at the strong red test color sample (TCS9) is a common recommendation for...Read More

CRI/Ra TCS spectrum data (CSV/Excel format)

We have published the CRI or Ra TCS (test color sample) spectrum data in 1 nm, 2 nm and 5 nm increments. There are a total of 8 regular test color samples, and 7 additional special test color samples. These samp...Read More

What is the difference between CRI and Ra?

When comparing lighting products, you will undoubtedly come across the metrics CRI and Ra to describe color quality. You may assume that there is no difference between CRI vs Ra, but read on to find out how this could be a mistake!   CRI defined CRI is an acronym for Color Renderin...Read More

Calculate color temperature (CCT) from CIE 1931 xy coordinates

Color temperature can be approximated using just a pair of xy coordinates from CIE 1931. Use the formula below, or simply plug in the x and y values into our online calculator. Looking to go the other way? See our CCT to CIE XY calculator....Read More

Color consistency in lighting products

For white LED lights, color consistency can be a critical but often overlooked quality that can make or break a project. Read on to learn how and why color variation exists, and how to ensure you can attain excellent color consistency for your LED light project! What exactly is color consistency? In g...Read More

What is CRI? The ultimate guide to the Color Rendering Index

Color Rendering Index (CRI) is an often misunderstood metric of color quality. Yet, for any application where color appearance is important, CRI consideration is critical. We've developed the following guide to help you understand what it is and how it can help you improve your quality of light. ...Read More

Calculate Duv from CIE 1931 xy coordinates

The Duv of a color point in a chromaticity coordinate system can be used to describe its distance from the black body curve. Duv can be approximated using just a pair of xy coordinates from CIE 1931. Use the formula below, or simply plug in the x and y values into our online calculator. CIE 1931 xy to Duv...Read More

Color matching function (X, Y, Z) values by wavelength (CSV/Excel format)

We have the color matching functions for each X, Y and Z available for download here. Click here to start the download in 1 nm increments.  ...Read More

Calculate Illuminant D SPD and CIE 1931 xy from color temperature

Illuminant D can be calculated from color temperature using our online calculator. Simply input the CCT and you will be able to download the corresponding Illuminant D spectral power distribution and CIE 1931 xy chromaticity point. Color temperature to Illuminant D SPD and CIE 1931 xy ...Read More

Calculate CIE 1931 xy coordinates from color temperature (CCT)

CIE 1931 xy coordinates can be approximated using color temperature (CCT). Simply plug in the CCT value into our online calculator. Looking to go the other way? See our CIE XY to CCT calculator. CCT to CIE 1...Read More