What's The Color Of This Dress?
Appelflap
This is a test
Huebidoo
Illuminant Catalog
Instructions
The library contains spectral data from light sources such as the Incandescent, Fluorescent, and LED Lamps. Some are measured using spectrometers, standardization organizations define others, and some are calculated from mathematical models. This app shows all the available illuminants in the form of their spectral distributions and primary colorimetric data.
Output
At start-up, the CIE F1 illuminant data are displayed. Its spectral distribution and name, Correlated Color Temperature, CIE Color Rendering Indices Ra and R9, and IES TM30 Rf and Rg are shown on top.
Correlated Color Temperature is given with unit Kelvin and includes a Tint value, with a unit of 1 corresponding to a distance of 0.001 in the CIE 1960 (u,v) color space. The CIE F1 illuminant, for example, has a correlated color temperature of 6425 Kelvin. It has a Tint of +7Δ, which means it is located above the Planckian locus, with a more blue/cyan-ish color than a Planckian radiator would have.
Its general color rendering index Ra value is 76, and its R9 value is -47. The R9 value indicates how well a source renderers deep red, an essential element of skin color, being the color of blood. A value of -47 is not very good; a value of at least 0, but preferably 20 or higher, is required if you want people to look not sick with your chosen light source.
Developed by Illumination Engineering Society (IES) members, TM30 is a new standard to evaluate a light source’s color fidelity and gamut. The F1 illuminant, for example, has a color fidelity Rf value of 81 and a gamut area index of Rg of 90. The Rf value is obtained from 99 instead of 8 test samples, as used for the CRI calculation, and is a better prediction of color rendering performance. The Gamut Area Index represents the ability of a light source to enhance colors in a scene: colors look more vibrant if this value is above 100. The CIE LED-RGB1 illuminant, for example, has a gamut area of 107.
Source Selection
Below the plot is the source selection area. The sources are grouped into different collections; currently, there are the “CIE” and “IES” collections. Select a collection by clicking on the first tab of the light source list. At start-up, the “CIE” collection is chosen.
Select a category within the library with the second tab. The available classes vary with the source library but typically describe the emission type of the sources, such as Fluorescent, Incandescent, High-Intensity Discharge, and LED. The illuminant within a category is selected by clicking one of the source buttons. The currently selected button is highlighted.
Access Spectral Data
The spectral data can be copied to your device’s clipboard by clicking the spectral plot area. A regular click will copy the data as two columns of values, with wavelengths, in nanometer units, in the first column, and spectral values in the second column. The values can be directly pasted into a spreadsheet if you want to do calculations yourself.
Spectral values are normalized to a peak value of 100.00 and are given with a three-decimal precision. Holding down the “shift”-key while clicking the spectral area will copy a single column of spectral data over a range from 380 to 780 nanometers, with a step size of 1 nanometer, resulting in a total of 401 copied values.
Troubleshooting
You must be online to use this app, as the spectral data are fetched from the website when selected. Please check your internet connection if you don’t see any spectral plot or sources in the list.
The site uses JavaScript, as many web apps do nowadays, but if you have disabled JavaScript support for this site, you need to enable it to use its functionality.
CIE Standard Illuminants
These are identified by one or more capital letters followed by zero or more digits. Typically, these sources, such as the equal energy E-illuminant, don’t exist in physical form and are mainly used for colorimetric research and as references.
Fluorescent (F-series)
The fluorescents here are distinguished by narrow-band and broad-band categories, referring to the spectral width of the phosphors used. F1-F6 fluorescent lamps emit two semi-broadband wavelengths of antimony and manganese activations in calcium halophosphate phosphor. F7-F9 are broadband fluorescent lamps with multiple phosphors and higher CRIs. At the same time, F10-F12 are narrow triband illuminants that emit three narrowband wavelengths in the visible spectrum’s R, G, and B regions.
High-Intensity Discharge (H-series)
The CIE defined five High-Intensity Discharge Standard Illuminants types using the letters H1-5.
LED
LED Standard Illuminants are defined as mixtures of Red, Green, Blue, Amber (RGBA) LEDS, Phosphor Converted (PC) LEDs, and combinations of both types (Hybrid). Five blue-pumped phosphor illuminants (B1-B5), two violet-pumped phosphor LEDs (V1-2), one RGB LED (RGB1), and one blue-pumped hybrid (BH1) LED Illuminants were defined.
Other
The A illuminant represents a tungsten filament lamp with a spectral power distribution similar to a Planckian radiator with a temperature of approximately 2856 Kelvin.
Historically, illuminants B and C were defined as physical standards obtained from an A illuminant using liquid filters to represent daylight. They are not commonly used anymore and are included here for historical reasons only.
Four specific daylight illuminants are defined, denoted by the codes D50, D55, D65, and D75, for daylight with correlated color temperatures of approximately 5000, 5500, 6500, and 7500 Kelvin.
IES TM30 Source Library
A team of scientists used the sources in this library to develop new metrics for light source color rendition, as described in a technical memorandum published by the Illuminating Engineering Society in 2015 and revised in 2018 and 2020. The collection at this site contains 318 spectral distributions. They are listed here using categories similar to the CIE standard illuminant library. It includes some CIE standard illuminants, actual measured spectral distributions, and spectral distributions based on mathematical models, such as distributions containing a mixture of Gaussian components balanced to a particular color point.
Fluorescent Broad-Band
Besides the CIE Standard Broad-Band Illuminants, this library adds measurements of 17 fluorescent lamps, primarily linear fluorescents, with different lengths, diameters, color temperatures, and color rendering indices.
The naming of Fluorescent lamps varies a bit by market and manufacturer, but typically, the first two numbers after the letter F indicate lamp power in units of Watts. Diameter, in units of 1/8 inch, follows after the letter T. Other letter combinations follow, with CW and WW, indicating Cool and Warm White color temperatures, and C75, a color temperature of approximately 7500K. For example, other letters indicate a Rapid Start (RS) lamp or the letter X for _De Luxe variants for better color rendering.
Fluorescent Narrow-Band
This category includes many more fluorescent lamps, combining three phosphors. Here, a code such as 735 indicates an illuminant with a CRI/Ra value of 70 and a color temperature of 3500K; a lamp with code 850 has a minimum CRI of 80 and a CCT of 5000K.
High-Intensity Discharge Lamps
Incandescent Lamps
Hybrid RGB(A)/PC LEDs
RGB(A) LED mixtures
Phosphor Converted LEDS
Mathematical Distributions
Other Lamps
CCT Calculator
Instructions
The CIE colorimetric system uses X, Y, and Z tristimulus values, calculated using spectral distributions and color-matching functions, as its basis for various colorimetric models. Lightsource chromaticity —or the color of “white” light— is typically expressed using a correlated color temperature and a —less commonly used— Tint value. Calculating these is complex. There is no simple mathematical formula: the method used here uses a high-accuracy bisectional search method.
Input are (X, Y, Z) tristimulus values, the default setting, or scaled (x,y) chromaticity coordinates, as used in the CIE 1931 chromaticity diagram.
The values are entered by selecting the input fields and typing the numbers.
The keyboard Enter-key will update the calculated values in the output display area.
The correlated color temperature has as unit Kelvin - the Tint value is unitless and is 1000x the distance from the color point to the Planckian curve, measured in the CIE1964 chromaticity diagram, which is sometimes referred to as milli-Δuv.
The initial values shown at start-up are the tri-stimulus values for the CIE D65 illuminant, with a Correlated Color Temperature of 6503.2K and a 3.2-Tint value, corresponding to a distance of Δuv = 0.0032 in the CIE 1964 diagram. Positive Tint values are above and appear more yellow-greenish, while negative values are below the Planckian Locus and typically appear more purple-pinkish.
By clicking the xy selection button, the input field changes to xy chromaticity coordinates, which are 0.31271 and 0.32903 for the D65 illuminant.
The temperature range of the implemented algorithm is 1000 Kelvin to 1,000,000 Kelvin; an error message indicates a temperature is too low or too high. The CIE definition of Correlated Color Temperature limits its calculation to a Tint range of -50 to 50, as it is a quantity mainly used for “whitish” light sources — an error message will be shown if that’s the case.
Invalid input will also result in error messages. Negative values are not allowed, as tristimulus and chromaticity values are always positive. Furthermore, chromaticity values x and y —lowercase— should be between 0 and 1, and their sum should be in this range too. There is no range limit in the tristimulus values, using the uppercase letters X, Y, and Z, except that they need to be positive.
Munsell Color Books
Instructions
This application displays the colors and spectral reflectivity data of the color samples found in Munsell Color books. For more background on Albert H. Munsell, his color books, and, most importantly, his color order system, see the Munsell Color System section below.
The plots shown are derived from measurements done by the University of Eastern Finland UEF and by Robin Myers, shared through his spectral library collection at Chromaxion. They can be used freely for personal, scientific, and educational purposes and redistributed only with attribution to their respective sources. Data from these sites were converted to spectral JSON files, the applications on this site.
Output
At start-up, the spectral composition of the sample with the highest chroma value of a Munsell Color Book page is shown, which is the 5R5/14 sample, a Burgundy red color. Its name, a circular color sample, three sets of chromaticity values, and spectral distribution are shown above a color patch selection box on the web page. The chromaticity values displayed here are the CAM16 UCS Ja’b’ values, using the CIE2015 10° standard observer, and the OKLCH lightness, chroma, and hue values and sRGB hex value using the CIE 1931 2° standard observer. For the most accurate colorimetric perception representation and color matching, use the CAM16 values; in digital applications, use the OKLCH or the sRGB hex values, preferably in that order.
Color Book Selection
Below the plot is the color patch selection area. This app has spectral data measured using different spectrometers and from different color books. On start-up, the data, as measured by the University of Eastern Finland, is shown using a Munsell Matte Color Book published in xxx, identified by the label UEF/Matte. The following color book collections are available:
- The University of Eastern Finland Collections, with the labels
- UEF/Matte
- UEF/Gloss
- and the Robin Myers — Chromaxion Collection:
- Chromaxion/Matte
- Chromaxion/Soil
The measurements are done on the actual samples of a colorbook, which can vary due to production tolerances and aging. Also, different instruments were used for the measurements.
Hue Selection
The Munsell color book typically contains forty pages, each containing samples with the same Hue. They are identified by a number, with a value of 1, 2.5, 5, 7.5, or 10, and an abbreviation of the color group with R for Red, YR for Yellow-Red, Y for Yellow, GY for Yellow-Green, G for Green, BG for Blue-Green, B for Blue, PB for Purple-Blue, P for Purple, and, finally, RP for Red-Purple. Select a page from this online color book with the second tab. The first page shown is 5R with a collection of red colors.
The samples within a page are ordered by Chroma value on the horizontal axis and Munsell Value (lightness) on the vertical axis. The Munsell value is a number between 1 and 10, placed directly after the Hue value, and the Chroma value is the value after the forward-slash separator. In the Munsell Color System, the Chroma value is unbounded at the high end, but here you’ll find maximum values of 14.
Access Spectral Data
The spectral data can be copied to your device’s clipboard by clicking the spectral plot area. A regular click will copy the data as two columns of values, with wavelengths, in nanometer units, in the first column and spectral values in the second column. The values can be directly pasted into a spreadsheet if you want to do calculations yourself.
Spectral values are normalized to a peak value of 100.00 and are given with a three-decimal precision. Holding down the “shift”-key while clicking the spectral area will copy a single column of spectral data over a range from 380 to 780 nanometers, with a step size of 1 nanometer, resulting in a total of 401 copied values.
Troubleshooting
You must be online to use this app, as the spectral data are fetched from the website when selected. Please check your internet connection if you don’t see any spectral plot or sources in the list.
The site uses JavaScript, as many web apps do nowadays, but if you have disabled JavaScript support for this site, you need to enable it to use its functionality.
A cut-out view of the three-dimensional shape of the Munsell color space, using cylindrical coordinates, with Hue (Color) as azimuth angle, Value (Lightness) as height (axial coordinate), and Chroma (Saturation) as radial distance.
The colors in this view are inaccurate and intended for illustration only.
Original by SharkD, CC BY-SA 3.0 , via Wikimedia Commons.
Munsell Color System
Albert H. Munsell (1858-1918) was a painter, teacher, and color scientist, mostly known for his color ordering system. He introduced his color system in his book A Color Notation in 1905. His first color book, Atlas of the Munsell Color System, was published in 1915. His last book, A Grammar of Color: Arrangements of Strathmore Papers in a Variety of Printed Color Combinations According to The Munsell Color System, was published after his death.
He founded the Munsell Color Company in 1917, a year before his death. His family later restructured it as the Munsell Color Foundation and Munsell Color Laboratory at the Rochester Institute of Technology. They are well known for producing the Munsell Books of Color, an improved version of the Atlas published by Albert Munsell in 1915, the Munsell Color Tree, and the Farnsworth Munsell 100 Hue Color Vision Test. Although the foundation closed in 1983, the X-Rite company still produces and sells these products under the Munsell product name.
He created an atlas of color, or color book, consisting of a collection of different painted color patches, categorized by the parameters Hue, or color in colloquial language, Value, typically called brightness, and Chroma or color saturation. Based on color perception experiments, the samples were created to have approximately the same perceptual color differences as their neighbors. He was not the first to propose these perceptual color parameters, as Grassmann used them in his first color law in 1853. Still, he was the first to create a systematic collection based on perceptual color differences using a systematic color notation.
In the Munsell color ordering system, a hue is identified by a number, ranging from 1 to 10, and a letter combination, as shown in the second tab of the color selection box above. The 1929 edition of the Munsell color book contained matte color samples and had 20 hue pages, identified by the numbers 5 or 10 and ten letter combinations. Later versions added pages with the numbers 2.5 and 7.5, resulting in 40 hue pages.
Besides Hue, colors are categorized by Chroma (color saturation) and value (brightness/lightness). Values range from 1 to 9, with 0 and 10 representing perfect black and white, which are not part of the color books as they are mathematically defined only.
Chroma values start at 0 for the grey samples and have varying maximum values. For 5R-hue in this application, it is 14, but values may extend the value of 20 for very pure colors.