TUTORIALS

The following documents contain technical presentations related to the quantitative description and measurement of color. Click on their title to view the document in your Web-browser or right-click to download. Except where noted, all downloadable files are in PDF format and require the free Adobe Acrobat Reader or Web-browser plug-in, version 5.0 or newer.

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Application Notes Color Theory RGB Spaces Tutorials Click on the following image to go to the Acrobat Reader Web site:

Application Notes

Illumination measurements

• AN-13 Adding DMX512 control to the high quality illumination lamp of AN-12 (4.7 MB) (New - June 2021) This document presents the components we added to the lamp described in AN-12 in order to control it from a computer using the DMX512 protocol. More specifically, we added a 5 Channels DMX512 LED Decoder (YJ-DMX-5C-G01) from Yujileds and a USB/Ethernet DMX512 Controller (ultraDMX2 PRO) manufactured by DMXking.com. The document explains how to configure the components and the DMX512 network and how to compute the control signal values corresponding to prescribed CCTs (Correlated Color Temperatures) with the same brightness for all CCTs. A sample measurements file and a Microsoft Excel spreadsheet file used to process the measurements is included in the downloadable package. In addition, fixture files and examples of program files are provided for two DMX512 control software, FreeStyler and Q Light Controller Plus (QLC+). • AN-12 Design and test of a high quality illumination lamp for color samples and prints (28.1 MB) (March 2021) This exaustive document describes how we built and tested a variable CCT illuminator based on a bi- color LED strip manufactured by Yujileds (Yujileds store). The CCT is adjustable between 2841 K and 6843 K (a spectrocolorimeter, such as an X-Rite i1Pro with ambient adapter, and software, such as BabelColor CT&A, is required to set the CCT). It achieves a brightness of 2000 lux at a 469 mm working distance and 500 lux at 938 mm. The usable work area is a circle with a diameter equal to 75% of the working distance (in the work area, the brightness is within 75% of the center brightness). The TM-30-18/TM-30-20 Fidelity level is F1 at all CCTs. While this iluminator does not emit in the UV range, its color rendering performance is on par with the best commercial light-booths, at a fraction of the price (some assembly required!). • Spectral Power Distributions (SPD) of 500+ light sources used to develop the TM-30-15 Method (330 KB) (July 2016) This file is a compressed zipped archive. The data is presented in Tab-delimited text files in which the SPDs are grouped by lamp categories; the SPDs are provided between 380 nm and 780 nm at 5 nm intervals. These files can be opened in a word processor, a spreadsheet application or with BabelColor CT&A CRI tools. The SPDs were those employed in: “Review of measures for light-source color rendition and considerations for a two-measure system for characterizing color rendition,” Kevin W. Houser, Minchen Wei, Aurélien David, Michael R. Krames, and Xiangyou Sharon Shen; Optics Express, Vol. 21, Issue 8, pp. 10393-10411 (2013); http://dx.doi.org/10.1364/OE.21.010393 • AN-11 The effects of a 10 nm bandwidth on data derived from spectrophotometer measurements (307 KB) (June 2016) This short document provides an estimate of the bias introduced by 10 nm measurements in the values computed for the ISO 23603 MI and the TM- 30-15 Fidelity and Gamut indices. The estimate is based on the results obtained with the spectrums of thirty (30) light sources with Correlated Color Temperatures (CCTs) around 5000 K, with CCT values ranging between 4747 K and 5364 K. • Light under control! (890 KB) (Written in collaboration with Roger Breton) We measured the characteristics of two fluorescent tubes designed for color rendering, one light booth designed for both direct view and transparencies viewing, and a SoLux tungsten bulb designed to reproduce daylight. We describe how to use the spectrum, the CCT, the chromaticity, the CRI, the Quality Grade of daylight simulators (as per CIE 51 / CIE S 012), and the illumination uniformity data to evaluate an illumination system. The document includes a presentation of ISO 3664 and its principal specifications.

White Balance targets

• AN-1 How to use a target for white balancing in RAW file import (708 KB) How to balance your white and adjust your exposure when opening a RAW file. Specific examples are given using Adobe Camera Raw (ACR) and Bibble, from Bibble Labs, purchased by Corel. • AN-2 How to use a white target to identify UV- enhanced paper (342 KB) The problems (and the few advantages!) of UV- enhanced papers, and how to identify them using a white target. No need for a colorimeter or spectrometer; a target plus your eyes or a camera are sufficient. You may also be interested in a Note on OBA (Optical Brightening Agents), written by Uwe Steinmueller of Digital Outback Photo, and see his test with the BabelColor white target.

Printer and Monitor proofing

• AN-3a Using PatchTool for IDEAlliance PRINTER proofing certification (854 KB) (Revised - April 2009) A description of Idealliance Hard Copy proofing requirements and an illustrated step-by-step presentation on how to use PatchTool to check your printer or press colorimetric accuracy. • AN-4a Using PatchTool for IDEAlliance MONITOR proofing certification (596 KB) (Revised - April 2009) A description of Idealliance Monitor proofing requirements and an illustrated step-by-step presentation on how to use PatchTool to measure and check your monitor colorimetric accuracy.

Miscellaneous

• AN-5 Taking back control of an IT8 7-4 file with wrong patch IDs (674 KB) (April 2009) Many IT8.7/4 files are saved with the patches in an order corresponding to the random or visual layout, but with improper IDs. The problem becomes more difficult to handle when the file was generated from measurements, and from a random layout, where the rows may have been scanned backwards, or where the rows were considered columns, and vice- versa. This Application Notes shows how to use PatchTool to fix most of these files. • AN-6 Evaluating an ICC profile coverage of the Pantone and IDEAlliance data sets (1.3 MB) (April 2009) A method, using PatchTool Gamut Tools Clip check, to evaluate if a list of colors will accurately be printed by a press or printer. Examples are given with the Pantone Coated and Idealliance SWOP Coated-3 data sets. The application note includes an Appendix which provides additional information on profile conversion accuracy. • AN-7 The Optical Society of America Uniform Color Scales (OSA UCS) (517 KB) (September 2009) This very comprehensive Application Note describes the structure and geometry of the Optical Society of America Uniform Color Scales (OSA UCS). The document contains examples of how to navigate within this color space and presents many color scales (color ramps) images which can be generated with PatchTool. The document includes four mini- tutorials. In particular, one tutorial shows how to generate a uniform list of colors which completely fills the gamut of a device profile; such a list can then be used to check a monitor's accuracy with PatchTool Display-Check for instance. Another tutorial shows how to compare the gamut of two devices in specific color ranges. Note: This Application Note can also be found as Appendix F of the PatchTool Help manual. • AN-8 How to optimize the accuracy of fluorescence measurements with BabelColor CT&A (303 KB) (January 2011) This application note discusses the parameters which can influence fluorescence measurements of printing papers. Potential problems are highlighted and a method to solve or identify them is proposed. It also presents a step-by-step procedure for optimal results. • AN-9a How to derive and use a Color Correction Matrix to improve display measurements (700 KB) (Revised - February 2012) This Application Note shows how to obtain a Color Correction Matrix between two instruments (a REFERENCE and a TARGET) as per ASTM E1455-2010 with the PatchTool Correction Matrix tool. Display measurements done with both instruments are presented. We see how the TARGET instrument measurements match those of the REFERENCE instrument when they are processed with a Color Correction Matrix. • AN-10 Exporting to the CxF3 and i1Profiler file formats with PatchTool (1.4 MB) (October 2013) PatchTool can export to generic CxF3 files as well as several CxF3-compliant file types used by X-Rite's i1Profiler. This Application Note presents PatchTool's CxF3 export features while highlighting the differences of the various i1Profiler file formats. Examples are shown for X-Rite's i1Profiler "Measure Chart" and "Profiling" workflows.

Color Theory

The CT&A Help manual contains many sections dedicated to technical information, including detailed equations for all color difference formulas and conversion between color spaces (L*a*b*, xyY, etc.), and ten tutorials: • CT&A Help manual (13.5 MB) A series of web tutorials published in 2004 on the graphics.com web site (now closed). Here are pdf versions of the original content. The RGB Code: The Mysteries of Color Revealed • Part 1: Cracking the RGB Color Code (from Light to XYZ) (302 KB) • Part 2: Cracking the RGB Code (From XYZ to RGB, and Other Codes) (386 KB) • Part 3: Color Differences and Converting Colors (316 KB) A series of articles in the Metal Finishing magazine (The articles used to be freely available; they need to be purchased now, sorry!): • Part 1: The Color of Money. Basic concepts: light, the eye, the Observer, gloss, numerical representations. Volume 103, Issue 1, January 2005, p. 38-42 • Part 2: Getting to Know the Language of Color. Color conversion, color decks, color difference, FED- STD-595 explained. Volume 103, Issue 2, February 2005, p. 36-39

RGB Spaces Tutorials

For the ones who want to gain a deeper knowledge of the mathematics behind RGB spaces, here are three "equation heavy" documents. There is overlap in the theory content; this was done so that they are self- contained. • RGB coordinates of the Macbeth ColorChecker (319 KB) (June 2006) The RGB coordinates of the ColorChecker in 4 RGB spaces (Apple, Adobe, ProPhoto, and sRGB), and the method by which they were derived from L*a*b* D50 data. For simulated (synthetic) images of the ColorChecker in the 4 RGB spaces presented in the above document, as well as in L*a*b* space, go to Page-2 of the ColorChecker pages. For additional information: ColorChecker_RGB_and_spectra.xls (155 KB .zip) (Updated - April 2012) This Excel spreadsheet contains: o RGB tables for 19 spaces, and L*a*b* (D50) values derived from averaged spectrums; o RGB tables for 19 spaces, and xyY (D50) values derived from GretagMacbeth L*a*b* D50 data (2005); o RGB tables for 19 spaces, and L*a*b* (D50) values derived from CIE (1931) xyY data (1976); o averaged spectral data with Standard Deviation tables (from 30 charts); o graphs of all the average spectrums with standard deviation. • A comparison of four multimedia RGB spaces (560 KB) Adobe (1998), Apple RGB, ColorMatch and sRGB compared. Which of the last three has the largest gamut? The answer may not be what you think! • A review of RGB color spaces (984 KB) The complete process between spectral data and RGB coordinates, from xyY to R'G'B', with a section on the various TV and multimedia display standards.