4 Colour Measurement and Digital Colour 

This section concerns additive mixture, colorimetry, digital colour spaces, and additive technology in graphics,  photography, and video.

Additive Mixture

Websites

The dimensions of colour, Section 4 - Additive mixing (David Briggs)

• http://www.huevaluechroma.com/041.php (additive primaries)

• http://www.huevaluechroma.com/042.php (additive mixtures)

• http://www.huevaluechroma.com/043.php (additive complementaries)

• http://www.huevaluechroma.com/044.php (additive-averaging and pointillist mixing)

ISLE | Chapter 6 | Additive color mixing 

• https://isle.hanover.edu/Ch06Color/Ch06ColorMixerAdd.html 

• Interactive demonstration of RGB additive mixing

Handprint (Bruce MacEvoy)

• https://www.handprint.com/HP/WCL/color5.html#theoryadd

Colour theory in two minutes (Stephen Westland)

• https://colourware.org/2018/06/24/4-additive-colour-mixing/  (4. Additive Colour Mixing)

• https://colourware.org/2018/07/03/9-optimal-additive-primaries/ (9. Optimal Additive Primaries)

Apps

RGB -colors mixer (dmyTRUEk)

• https://play.google.com/store/apps/details?id=dmytruek.rgb 

• Simple free RGB mixing app.

Color match RGB (Arte Digital)

• https://play.google.com/store/apps/details?id=mx.com.artedigital.RGBColorMatch 

• Free RGB mixing app with colour matching challenge.

CIE Colorimetry

A beginner’s guide to (CIE) colorimetry (Chandler Abraham)

• https://medium.com/hipster-color-science/a-beginners-guide-to-colorimetry-401f1830b65a 

How the CIE 1931 RGB Color Matching Functions Were Developed from the Initial Color Matching Experiments (Yuhao Zhu, @yzhu88)

• http://yuhaozhu.com/blog/cmf.html

Interactive Tutorials on Color Science Basics (Yuhao Zhu, @yzhu88)

• A set of interactive tutorials in the form of Web apps that help understand basic concepts in color science originally developed for the Mobile Visual Computing course taught at University of Rochester by Yuhao Zhu.

• https://horizon-lab.org/colorvis/

Color vision (Craig Blackwell)

• https://www.youtube.com/watch?v=82ItpxqPP4I (Color Vision 2: Color Matching)

• https://www.youtube.com/watch?v=KDiTxWcD3ZE (Color Vision 3: Color Map)

Introduction to color theory (Mark Levoy, Katie Dektar) 

• https://graphics.stanford.edu/courses/cs178/applets/locus.html  (excellent Flash apps, still working with Ruffle Flash emulator)

Emulating the Wright-Guild experiment (Edgardo García. MSEng, Buenos Aires University) 

• http://rgbcmyk.com.ar/en/emulating-the-wright-guild-experiment/

Principles of light and color measurement (Radiant Vision Systems, 2018)

• https://www.youtube.com/watch?v=SEziy_HHBU0 

Useful color data (Munsell Color Science Lab, RIT)

• https://www.rit.edu/science/munsell-color-science-lab-educational-resources#useful-color-data 

Color Converter (Robin Myers) 

• https://web.archive.org/web/20160331060152/http://rmimaging.com/Color_Converter_2.3.zip  (Windows/Mac)

• A utility program for converting colors between XYZ, xyY, Lab, LCH(ab), Luv, LCH(uv) color spaces. You can set it to convert with over a dozen white point settings, including your own custom white points.

CIECAM02 Plug-In (Cliff Rames)

• https://sites.google.com/site/clifframes/ciecam02plugin

• Interactive exploration of the CIECAM02 model. 

LED ColorCalculator (Osram)

• "The ColorCalculator software is a standalone program that allows designers to estimate the photometric performance of color mixing schemes. Designers can mix standard LEDs and calculate photometry of the resultant light. An optimization function is also available to adjust a design to user specified photometry target".

• https://web.archive.org/web/20230603145639/https://www.osram.us/cb/tools-and-resources/applications/led-colorcalculator/index.jsp

Handprint (Bruce MacEvoy)

• https://www.handprint.com/HP/WCL/color6.html#colorimetry (colorimetry)

• https://www.handprint.com/HP/WCL/color7.html (modern color models)

CIELAB & CAM02 color picker (Bastien Dejean)

• https://rufflewind.com/_urandom/colorpicker/

Visualizing the XYZ color space (Sony)

• https://www.youtube.com/watch?v=x0-qoXOCOow 

• Outstanding video of CIE XYZ in relation to other colour spaces

The CIELAB lecture (John Seymour)

• https://youtu.be/sk8NC740SFY

Digital Colour Specification and Spaces

Color topics for programmers  (Peter Occil)

• https://www.codeproject.com/Articles/1202772/Color-Topics-for-Programmers

Color spaces (Bartosz Ciechanowski) 

• https://ciechanow.ski/color-spaces/ 

• Article incorporates excellent interactive demonstrations

Gamma FAQ (Charles Poynton)

• http://www.poynton.com/PDFs/GammaFAQ.pdf

Color FAQ (Charles Poynton)

• http://www.poynton.com/PDFs/ColorFAQ.pdf

Introduction to video color spaces  (Charles Poynton)

• https://groups.google.com/g/rec.video/c/mFUxqWF44io/m/He5ZJAj1EqUJ?pli=1

The representation of color metrics and mappings in perceptual color space (Stephen Boker).

• https://web.archive.org/web/20210416195837/http://people.virginia.edu/~smb3u/ColorVision2/ColorVision2.html

The color guide and glossary (Xrite).

• https://web.archive.org/web/20100704165158/http://www.xrite.com/documents/literature/en/L11-029_color_guide_en.pdf 

Light and color: an introduction (Norman Koren): Relatively simple introduction to colour spaces for digital photographers/artists.

• http://www.normankoren.com/light_color.html

Graphics short course I: color theory and 2D image representation.

• https://web.archive.org/web/20170111093014/http://viz.aset.psu.edu/gho/sem_notes/color_2d/index.html 

Color: from hexcodes to eyeballs (Jamie Wong)

• http://jamie-wong.com/post/color/ 

• Mostly very good (but should have looked up what wavelengths a lemon reflects!).

Exploring color theory with Blender (Mark Meyer)

• http://www.photo-mark.com/notes/color-theory-blender/

Visual representation of color names in different color spaces  (David A., Codepen)

• https://codepen.io/meodai/full/zdgXJj 

A perceptual color space for image processing (Björn Ottosson)

• https://bottosson.github.io/posts/oklab/

Color playground (Alexey Ardov) @ardovalexey

• https://color-playground.ardov.me/spaces-3d

• https://hueplot.ardov.me/

• Interactive display of very up-to-date range of colour spaces.

Online and Offline Conversion Programs

Virtual Atlas (VCS Consulting)

• "This free web application (IE, Safari and Chrome compatible) provides virtual colour atlases for the Colorcurve, Coloroid, DIN-6164, Munsell, NCS, OSA-UCS, and Swiss Colour Atlas 2541 colour order systems and for the BS:5252, RAL-840HR, and RAL-841GL colour ranges. In addition, the application supports spectral curve calculation, colour difference calculation, colour comparison, and colour notation conversion. Each colour atlas can be viewed in a range of different planes, for example Munsell can be viewed as planes of constant hue, value, or chroma, and each plane can be magnified up to 800% displaying calculated intermediate colours not present in the actual atlas."

• http://www.vcsconsulting.co.uk/Colour/colour.html

• https://virtualatlasblazor.azurewebsites.net/

Color Atlas (Harald Brendel)

• http://color.support/coloratlas.html

• Interactive atlas displaying and exporting adjustable vertical slices through CIE L*a*b*, CIE L*u*v*, CIECAM 02, IPT (Ebner and Fairchild, 1998), YCbCr and HSV. 

Color calculators and spreadsheets (Bruce Lindbloom).

• http://www.brucelindbloom.com/index.html 

• Select "Calc", "Info" or "Math" at the top of the page for various useful features including:

• CIE Color Calculator: Converts among most of the CIE color models (XYZ, xyY, Lab, LCH(ab), Luv, and LCH(uv)),  as well as providing correlated color temperature and standard RGB conversions.

• Color Difference Calculator: Computes color differences using several different methods (Delta E, CIE94, CMC).

• Spectral Calculator Spreadsheets: Calculates colorimetry, densitometry and RGB values from your spectral data. 

• ColorChecker RGB Summaries, Spreadsheets and Lab TIFF File: You will find three things on this page, a) summaries of the ColorChecker colors, expressed in each of many standard RGB color spaces, b) spreadsheets that allow you to findhich RGB color space is closest to your RGB values, and c) a computer generated Lab TIFF file of the ColorChecker.

• Dot Gain from Lab or Profile: Two spreadsheets which calculate dot gain from Lab measurements, also allowing you to measure the dot gain of a CMYK ICC printer profile.

• ColorChecker Calculator: Performs many spectral calculations on the 24 colors of the ColorChecker chart.

• Chromatic Adaptation Calculator: Converts colors between reference whites using different chromatic adaptation algorithms.

• Color Difference Calculator.

• Formerly available features not currently on site (2020) include;  Companding Calculator: Converts among luminance, CIE L*, density and gamma. Includes both a numeric calculator and a graphical display. CIE Spectral Display: Calculates and displays many useful CIE functions, such as the Standard Observers, the Standard Illuminants and blackbody radiators. Levels Calculator: See how you lose levels when you pass data through curves. Munsell Display Calculator: Displays the Munsell color set (2734 colors) in xyY, Lab and Luv. This is a useful tool for evaluating uniform perceptual color spaces. Also included is an explanation of the infamous "blue turns purple" problem often seen with printer profiles. Dot Gain Calculator: Performs the standard Murray-Davies dot gain equation to your density measurements.

Color Inspector 3D

• http://home.htw-berlin.de/~barthel/ImageJ/ColorInspector/help.htm 

• https://imagej.net/Color_Inspector_3D (Color Inspector 3D plugin for ImageJ)

• Standalone program and plugin for interactive visualization of image data in various color spaces. Very highly recommended.

Artists' Helper (Robert Burrage)

• https://www.artistshelper.com/p/helpers.html

• Among other uses, displays image colours in various colour spaces. Less intuitive to use than Color Inspector 3D but output is much more aesthetically pleasing.

Convert color data into different standards and color spaces (EasyRGB)

• https://www.easyrgb.com/en/convert.php 

• Interconvert sRGB <> sRGB   0-1.0 <> RGB Adobe 98 <> HSL <> HSV <> HSI <> CMY <> CMYK <> CMYK <> XYZ <> Yxy <> L*ab <> L*Ch(ab) <> L*uv <> L*Ch(uv) <> HunterLab and to match color data to color cards, paint lines, inks, fandecks, standards and other real world products and references.

Leonardo (Nate Baldwin)

• https://medium.com/@NateBaldwin/leonardo-an-open-source-contrast-based-color-generator-92d61b6521d2

• https://leonardocolor.io/#

KGamut2 gamut tool (Cristian Romero)

• http://cr10blog.blogspot.com.au/2013/02/kgamut.html

Colorimeter (Android app)

• https://play.google.com/store/apps/details?id=com.colorimeter

Color Analysis (Android app)

• https://play.google.com/store/apps/details?id=com.color.coloration

Color Extractor (Android app)

• https://play.google.com/store/apps/details?id=jp.beingtested.ColorExtractor

Color Sliderule (Axiphos)

• http://www.axiphos.com/Software/software.html

• "This freeware package performs conversion of color data between different expressions for a given illuminant and observer, including also whiteness data. Conversions are possible between (Rx,Ry,Rz), (X,Y,Z), (Y,x,y), CIE-L*a*b*, Hunter-Lab, RGB, sRGB, Whiteness CIE and dominant wavelength and vice versa. Whiteness equations include whiteness indices after CIE, Ganz-Griesser (nominal parameters), Uchida, Berger, Stensby, Hunter, ASTM, Croes, Taube, Stephanson and Harrison; also yellowness index can be calculated." 

Color conversions (Per Bang)

• http://www.perbang.dk/rgb/00E52A/

• RGB <> Hexdecimal <> CMYK <> HSV <> HSL <> CIE-L*ab <> XYZ + Munsell, NCS, Pantone, RAL Classic etc.

Working with color

• http://www.workwithcolor.com/color-converter-01.htm

• http://www.workwithcolor.com/hsl-color-picker-01.htm

• http://www.workwithcolor.com/mm-color-blender-01.htm

• RGB <> HSB <> HSL<> CMYK(simple) <> CIE L*a*b* <>HSL <> Hex

Introduction to color (Eugene Vishnevsky): 

• http://www.cs.rit.edu/~ncs/color/

• Online Java applets explaining colour spaces.

Colorizer

• http://colorizer.org/ 

• "Color picker, calculator and generator with high precision and contrast test. Converts also RGB, HEX, HSL, HSV/HSB, CMYK and CIE-LAB colors and lots of other formats". 

Color Converter

• http://colormine.org/color-converter 

• "Select a color space and enter your values for accurately convert your selection to Rgb, Cmy, Cmyk, Hsl, Xyz, Lab, Lch and Yxy". 

CMM Color Engine (Little CMS)

• https://littlecms.com/color-engine/ 

• "Open source small-footprint color management engine, with special focus on accuracy and speed. It fully supports all kind of V2 and V4 profiles, including abstract, devicelink and named color profiles. Free under MIT License". 

• Site also hosts commercial software including Color Translator, a "tool for color conversion on TIFF, JPEG, PNG, OpenEXR and PDF files. Batch conversion on file lists or hot-folders. It can deal with RGB, CMYK, Lab, black-preservation, smart intents, abstract profile adjustment chains, linear light color spaces and many, many more. Demo version works for free on files under 60K".

RGB colorspace transformation matrix and chromatically adapted primaries (color-science.org)

• https://www.colour-science.org:8010/ 

Color space conversions (github.com/colorjs/ )

• http://colorjs.github.io/color-space/#ff2030 

• Interconversion of 18 colour spaces

3D Gamut Viewer (PerfX )

• https://web.archive.org/web/20080511211242/http://www.tglc.com/english/PerfX/3D_Gamut_Viewer.html 

HCL Wizard

• http://hclwizard.org/ 

• Includes Palette Creator, Deficiency Emulator and Color picker online apps

Additive Technology

Under construction! Please see also Digital Colour Spaces and Online and Offline  Programs on 1 Colour Attributes and Colour Spaces.

 The Hitchhiker's Guide to Digital Colour (Troy Sobotka @troy_s)

• https://hg2dc.com/

• Includes a superbly presented and authoritative step-by-step introduction to digital colour,. followed by some stimulating explorations of more controversial questions.

Myndex

• https://git.myndex.com/

• Massive catalog of Myndex Research content, including APCA articles & documentation, related code repositories, and great resources on visual perception relevant to legibility of text.

Color & Contrast (Nate Baldwin)

• https://colorandcontrast.com/#/

• New site full of excellent explanations and interactive demonstrations on topics from physiology of the eye through to colour spaces, colour formulae, device colour modes and UI & data visualization.

Colorwiki (CHROMIX Inc.)

• http://www.colorwiki.com/wiki/ColorWiki_Home 

• Mix of user-edited and authored articles mainly concerned with colour management.

John the Math Guy (John Seymour) 

• http://johnthemathguy.blogspot.com.au/

• "Applied math and color science with a liberal sprinkling of goofy humor".

Colour science

• https://www.colour-science.org/ e.g.:

• https://www.colour-science.org/posts/the-importance-of-terminology-and-srgb-uncertainty/ 

Nine degrees below (Elle Stone)

• https://ninedegreesbelow.com/ especially:  

• https://ninedegreesbelow.com/photography/articles.html (articles on colour management)

• https://ninedegreesbelow.com/photography/xyz-rgb.html (painless Guide to XYZ, RGB, ICC, xyY, and TRCs)

• Color management, photography and painting using free/libre software.

Color management and colorimetry (Marcelo Copetti, in Portuguese)

• https://marcelocopetti.blogspot.com/ 

Introduction to color in digital filmmaking  (Filmmaker IQ)

• https://www.youtube.com/watch?v=v7MdPJqEOU4 

Academy Color Encoding System (ACES) forum

• https://community.acescentral.com/ 

• See also the ACES YouTube channel.

An interactive review of Oklab (Ralph Leviens)

• https://raphlinus.github.io/color/2021/01/18/oklab-critique.html

Perceptually uniform color models and their implications (Max Bo)

https://observablehq.com/@mjbo/perceptually-uniform-color-models

FilmLight

• https://www.filmlight.ltd.uk/watch/watch.php

• Growing collection of videos on various aspects of digital colour technology in cinema

The Pointer's gamut (Kid Jansen)

• https://www.tftcentral.co.uk/articles/pointers_gamut.htm 

• The coverage, in terms of chromaticity, of real surface colors by RGB color spaces and wide gamut displays.

 Applied color theory in Photoshop (Dan Margulis) 

• https://groups.io/g/colortheory 

• Discussion group

The first ten years of Photoshop (Jeff Schewe)

• http://www.schewephoto.com/pei/pshistory.pdf