220824, Server1: http://farbe.li.tu-berlin.de/index.html or Server2: http://color.li.tu-berlin.de/index.html
An alternate URL for the Server2 is since 2010 http://130.149.60.45/~farbmetrik/index.html

For this page of this TUB web site (NOT archive), see
index.html in English, or indexDE.html in German.

For a page with additional information, see
index+ in English, or indexDE+ in German.

For the archive information (2000-2009) of the BAM server "www.ps.bam.de" (2000-2018) about colour test charts, colorimetric calculations, standards, and publications, see
A/indexAE.html in English, or A/indexAG.html in German.

For links to the chapter A Colour Image Technology and Colour Management, see
Content list of chapter A: AEA_I in English or AGA_I in German.
Summary of chapter A: AEA_S in English or AGA_S in German.
Example content part AEAI of 26 parts AEAI to AEZI: AEAI in English or AGAI in German.
Example images part AEAS of 26 parts AEAS to AEZS: AEAS in English or AGAS in German.

For links to the chapter B Colour Vision and Colorimetry, see
Content list of chapter B: BEA_I in English or BGA_I in German.
Summary of chapter B: BEA_S in English or BGA_S in German.
Example content part BEAI of 26 parts BEAI to BEZI: BEAI in English or BGAI in German.
Example images part BEAS of 26 parts BEAS to BEZS: BEAS in English or BGAS in German.

For links to the chapter C Colour Spaces, Colour Differences, and Line Elements, under work, see
Content list of chapter C: CEA_I in English or CGA_I in German.
Summary of chapter C: CEA_S in English or CGA_S in German.
Example content part CEAI of 26 parts CEAI to CEZI: CEAI in English or CGAI in German.
Example images part CEAS of 26 parts CEAS to CEZS: CEAS in English or CGAS in German.

For links to the chapter D Colour Appearance, Elementary Colours, and Metrics, under work, see
Content list of chapter D: DEA_I in English or DGA_I in German.
Summary of chapter D: DEA_S in English or DGA_S in German.
Example content part DEAI of 26 parts DEAI to DEZI: DEAI in English or DGAI in German.
Example images part DEAS of 26 parts DEAS to DEZS: DEAS in English or DGAS in German.

Welcome to a website colorimetry and colour image technology


This web site has been created by Prof. Dr. Klaus Richter, Berlin University of Technology (TUB), section Lighting Technology, see
homepageTUL

The logo of the book with the title "Colorimetry and Computer Graphics" (in German) with about 500 colour figures of Klaus Richter is shown.
For order and/or download see buche

You may reach the author by:
email: klaus.richter@mac.com
mail adress: Prof. Dr. Klaus Richter, Walterhoeferstrasse 44, D-14165 Berlin, Germany

For a list of recent publications and oral presentations at meetings of the Research Group "Berlin University of Technology, Section Lighting Technology, Teaching area Colorimetry and Image Technology" see
XY91FEN
This website includes remarks about recent publications.
Intended workshops and presentations at future colour meetings are announced.
This page includes contents for Zoom meetings on colour and applications, and for the registration.

Structure and content of this web site with different parts

Figure 1: Top structure of this web site.
For the download of this figure in the VG-PDF format, see AEX00-8N.PDF.
The PDF format in vector graphic (VG) gives always the best readability.

Figure 1 lists the information on this server:
For example Part A includes on the pages with the names A(G/E)(A..Z)(I/S/0..9).HTM
about 4000 figures with english and german text.

Therefore the Server1 and the Server2 with approximately the same content seem
to be important for the scientific basis and applications of the above topics.

The development of this web site is connected with the author Klaus Richter.
His PhD thesis was published in 1969 by the University of Basel (Switzerland):
"Antagonistic signals in colour vision and relation to the perceived colour order".
This PhD paper (in German) is available under "publications", see XY91FEN

In 2019 the following TUB-project title was decided:
Colour and colour vision with Ostwald device and elementary colours -
Antagonistic colour-vision model and properties for many applications.


This TUB project consist of four parts:
A. Colour Image Technology and Colour Management (2019),

Summary: AEA_S in English or AGA_S in German.

B. Colour Vision and Colorimetry (2020),
Summary: CBEA_S in English or BGA_S in German.

C. Colour Spaces, Colour Differences, and Line Elements (2021),
Summary: CEA_S in English or CGA_S in German.

D. Colour Appearance, Elementary Colours, and Metrics (2022, under work).
Summary: DEA_S in English or DGA_S in German.

In 2022 special properties of colour vision were considered in a paper:
TUB-relativity model of colour vision for light and surface colours.
see: farbe2207.pdf in English or farbg2207.pdf in German.

1. Antagonistic and TUB-relativity model of colour vision
The TUB-project title includes the term "antagonistic" of the Greek language. This term is well known in medicine for muscles. The muscles may work in "antagonistic" (or opponent) directions.

Colours may have "antagonistic" properties, which for example can be described by "opponent", "complementary", "compensatory", "shadow effect", "after image effect", "successive contrast", and "simultan contrast".

The "antagonistic" colour appearance attributes can be described for example by
"lightness - darkness", "blackness - brilliantness", "whiteness - deepness", "chromaticness - achromaticness".

These attributes change for example with the reflection of the ambient light on the display, compare the properties for eight reflections:
OE73/OE73F1P0.PDF.

The question arises, if an "antagonistic" colorimetry is able to describe many colour effects and colour appearance attributes. These affects and attributes are applied in the area of design, architecture, and art, and for example in the Swedish "Natural Colour System NCS".

It is believed that the visual system of man constantly adapts to a "medium" achromatic stimulus with a "medium" luminance of the visual scene. Based on the TUB colour vision modell, all light and surface colour sensations are calculated relative to these "average" measurable data of colour and light.

For example the TUB-relativity model of colour vision calculates equal hue thresholds for complementary optimal and display colours in agreement with experimental results of Holtsmark and Valberg (1969). For properties of this model see the papers marked with a *) under XY91FEN

In applications a ISO-colour loop plays an increasing roll. Effective information is possible from a pdf file with a pdf reader. The links in the image are only working from the downloaded pdf file with vector graphic, see ISOColorloopE.pdf

In the following as example a project application is described. This application is part of the ISO-colour loop for the display output at the ergonomic workplace. Unfortunately in 2022 after more as 20 years the company Apple has deleted the gamma slider, which is described in ISO 9241-306:2008 and ed-2:2018. This gamma slider is shown in the following.

In 2022 alternatives to the deleted slider applications of macOS have been presented. In addition new possibilities for the display output at the ergonomic workplace are created, see workshops http://www.deutsches-farbenzentrum.de

2. Ergonomic changes of the rgb*-colour output at office work places by power functions depending on the display reflection of the ambient light

The reflections of ambient light in offices change the display-output colours. About 3,6% reflection compared to the white display (90%) reduces the colour gamut to 50%. Often more important is the change of the colour spacing by the reflection of the ambient light. In a worse case the reflection of the ambient light may be 40% compared to the white displays. This happens with projectors in an office with much daylight or for displays with sunlight reflections.

In this worse case four dark of 16 grey steps may appear black and can not be distinguished. The visual equidistant spacing of a 16 step grey series without display reflections is therefore to a high degree destroyed.

If the rgb* values are changed by a power function one can make the 16 steps again visible and equally spaced. Appropriate rgb* changes increase the visibility and reduce visual fatique at any display-work place.

ISO EN DIN 9241-306:2018 defines 15 contrast steps for luminance between the High Dynamic Range (HDR) and the Low Dynamic Range (LDR). The colour gamut decreases from 100% to about 13% for a change of the contrast step between Cmax=288:1 and Cmin=2:1. Both the lightness and the chroma decreases.

For example for the display-output test, the ISO-test chart AE49 with 1080 colours has been developed. The output questions for the 15 contrast steps are given in English (E), German (G), and French (F).
The ISO-test charts are on the ISO Standards Maintenance Portal in the file formats PDF, and PostScript (PS, TXT), see
http://standards.iso.org/iso/9241/306/ed-2/index.html.


Figure 1: Test chart AE49 according to ISO 9241-306 with 1080 colours for 15 contrast steps
For the download of this figure in the VG-PDF format, see AEW8L0NP.PDF.

Instead of the 15 contrast step on 15 pages Fig. 1 includes the 15 contrast steps on one page and in addition one reference image (with a red frame). Usually by visual inspection only one of the 15 outputs shows the intended equal spacing of the colour steps. The visual spacing changes with the display reflection of the ambient light.

The test chart is designed for the relative gamma range 0,475 < gp < 2,105. This range corresponds to the (absolute) gamma range 1,20 < ga < 4,8. The gamma value g = 2,4 in the middle of this range is known from the lightness L*IECsRGB of the sRGB colour space according to IEC 61966-2-1, compare Fig. 40 and 44.

The above gamma range corresponds to the contrast range 2:1 < C < 4608:1. In offices the contrast C = 36:1 is the standard contrast for the displays and the paper. The standard contrast of the white and black paper is determined by the reflections R=0,90 and R=0,036. The reflection ratio defines the office contrast C = 36:1. The standard luminance of the display is LW=142 cd/m^2 for white and LW=4 cd/m^2 for black. The luminance ratio defines the office contrast C = 36:1.

The contrast C=36:1 has the name CP5 in ISO 9241-306 and produces the optimal readability and colour spacing in a standard office.

In ISO 9241-306:2008 and ed2:2018 a "Gamma slider" is described. The gamma slider serves for the creation of an equally spaced output of the reference ISO-test chart (with a red frame in Fig. 1). This is then also the recommended ergonomic output for the whole display.

With the "slider technology" the rgb* values are changed by a power function. With a power function the start-rgb* values 0, 0, 0 for Black N and 1, 1, 1 for White W will not change. However, for example the three start-rgb* values 0,5, 0,5, 0,5 change to the values 0,25, 0,25, 0,25 for the exponent k=2 or to the values 0,70, 0,70, 0,70 for exponent k=0,5.

Remarks:
Since 2000 macOS X includes a menu for the gamma slider. ISO 9241-306 describes the advantages of the gamma slider as example. The slider is available under "System Preferences - Display - Color - Calibrate".

Since 2020 (macOS 10.15) the slider is only available, if the "Alt-key" is pressed during the choise of "Calibrate".

Since 2022 (macOS 12.3) the option "Color" is deleted and the Slider for the ergonomic output is not any more available.

If after 20 years for the ergonomic output on display work places another solution will appear for the slider is unknown. Until a solution will appear one may still use macOS 11.

Under Windows there are many application programs, which may replace the slider, see RUSCHIN22.PDF.

For the download of 9 ICC profiles with the absolute gamma 1,0 <= ga <= 2,6, which can be tested as an alternative under macOS and Windows, see (94 KB) LCD_XX.zip.

Development goal:
16 Million rgb data are transfered to 16 Million rgb' data by colorimetric criteria. For many display applications a ColourConnectionSpace (CCS) is used for the calculation of the transformation. For this the relative equidistant TUBLAB colour space seems more appropriate compared to the CIELAB colour space. The transfer rgb to rgb' is possible for single and video images with the graphic card of a desktop computer.

The TUB-colour group appreciates information about appropriate application programms under Mac and/or Windows. The TUB group will support the distribution for ergonomic applications.

For many applications with the slider or altrnative methods see AEXI.HTM.


Figure 2: The gamma slider of the computer-operation system macOS X
For the download of this figure in the VG-PDF format, see AEX50-7N.PDF.

A gamma range 1,00 < g < 2,6 is used under macOS X to change the whole display output. For the ergonomic output Yes/No criteria come with the test chart AE49 of ISO 9241-306. For many ambient reflections and different default and real values of the display gamma, one position of the slider leads usually to an ergonomic display output.

Also if the display image for example appears under or over exposed, then the gamma slider can usually produce an ergonomic output. The output values rgb* = 0 0 0 for Black N and rgb* = 1 1 1 for White W are not changed by the slider, only all values between 0 and 1. However, if the rgb* values of black and white are NOT 0 and 1, then the values change.

Section AECI.HTM shows, how to normalise images in the case of under or over exposure.


Figure 3: 16 times the same test chart AE49 according to ISO 9241-306 with 1080 colours
For the download of this figure in the VG-PDF format, see AEW7L0NP.PDF.

The test chart is designed for the relative gamma gp=0,775. This corresponds to the contrast C=36:1. This contrast is called CP5 in ISO 9241-306 and produced the optimal readability and colour spacing in a standard office.

It is intended that users download the VG-PDF file of Fig. 50 for a visual test. Often the ambient reflections are different at the corners and in the middle of the display. Visual inspection can decide, if different readability or different colour spacing is visible. In this case one can look for solutions, for example by a position change of the luminaires or of the display.

Summary of the section 2
The free available ISO-test chart AG49 according to ISO 9241-306:2018 simulate in the PDF file eight contrasts, which are produced in the standard office by display reflections of the ambient light. Eight pages include image data between rgb* = (0 0 0) for Black N and rgb* = (1 1 1) for White W. Power functions change the rgb* data between 0 and 1, for example r*=0,5 with the power value k=2 to r*'=0,5^k = 0,25. With this the image looks darker or with k=0,5 it appears lighter.

For an ergonomic and equally spaced output the variables rgb*, R, Y, or L shall be changed by a power function with the exponent k in the case of a change of:
1. the display reflection by the ambient light
2. the surround from White W to Black N, see Fig. 40, 44 und 47, sowie
3. the colour-sample distance, see Fig. 41, 45, 46.

In image technology the rgb* data are changed by a gamma slider or in files by a power function with the exponent k. This change allows usually to reach the goal of an ergonomic and equally spaced ouput.

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For a page with additional information, see
index+ in English, or indexDE+ in German.

For this TUB web site (NOT archive), see
index.html in English, or indexDE.html in German.

For the archive information (2000-2009) of the BAM server "www.ps.bam.de" (2000-2018)
about colour test charts, colorimetric calculations, standards, and publications, see
indexAE.html in English, indexAG.html in German.

For similar Information of the BAM server "www.ps.bam.de" from the WBM server (WayBackMachine)
https://web.archive.org/web/20090402212108/http://www.ps.bam.de/index.html