II.C - Screen calibration

The very important first stage of color management in a production pipeline of digital images is to ensure the fidelity of the screens, that the colors displayed are the closest possible to what the images contain. It is the calibration process.

Calibration, by greatly improving the fidelity of the screens, makes it possible to have a correct display, even very good by using a probe, even on screens of lesser quality1.

C.1 - Introduction

The purpose of screen calibration is multiple:

The obstacles to achieving this are also multiple:

The most reliable way to do this is to rely on a calibration probe.
A probe is in fact a light sensor that works in tandem with the computer to apply color corrections, and its role is to measure the colors displayed by the screen, to compare with reference values. Most of the probes are also able to measure the ambient light to take into account the variations due to the environment and the human perception.

The use of a probe thus makes it possible to overcome all these obstacles:

Photo of a probe on a screen

However, in the absence of a probe, it is also possible to improve the display of colors with another sensor: the eye. The results will not be as precise as with a probe, but it’s possible to improve the display of the worst screens. The main problem of eyeballing is the lack of an objective reference to compare colors: it is impossible to be sure that the colors displayed are the right ones. The influence of the environment is also a problem, but can be compensated with good planning.

C.2 - Environment

First of all, a relatively easy parameter to control is the working environment and the ambient light in which the screen colors are seen.

A few simple rules can ensure that you always see the same colors, and as objectively as possible.

Here are the parameters of the environment such as it is recommended by the color space sRGB, that of the majority of the screens, and applicable to the other spaces (P3, Rec.2020…):

C.3 - Calibration

Once the environment has been controlled, or in any case set in the working conditions, we can proceed to the calibration of the screens.

Before starting, it is necessary to make sure of the parameters of the calibration to be done.

C.3.a - Choice of the screen color space and calibration

We choose default one, in general sRGB or sometimes Display P3 or more rarely others.

You can also decide to calibrate to a different space than the one intended for the screen, provided that the two spaces are compatible. This can be useful when all manufactured images are intended for a specific use (TV, cinema…) in order to work in the same or close to the space used for the broadcasting of the finished images. For example, screens can be calibrated in Rec.709 to make HD videos for TV and watch them in broadcast conditions, without having to convert the videos at playback time to the screen space2.

It is necessary for that that the primaries* of the two spaces are the same, or that the gamut* of the space of the screen is larger and contains the gamut of the space in which one calibrates. In any case, you should remember to change the display settings in all applications and the operating system so that the images are displayed in the space in which you have calibrated the screen.

The choice of space will define the primaries* and gama* used; the white point* can often be set separately.

C.3.b - White point and brightness

The white point is often adjustable when using a probe; unless there are specific needs such as work for printing (in which case the white point can be that of the paper), one chooses that of the colorimetric space of the screen, i.e. D65, 6500 K in the majority of the cases.

The luminosity can also often be measured and adjusted. When working for images in sRGB intended to be seen on a computer screen, the reference is 80 cd/m². For television work (or cinema), the luminosity can be that of Rec.709, that is 100 cd/m². It may be useful to choose a slightly higher value if the working environment is too bright.

C.3.c - Calibration and application of the color profile

C.3.c.1 - Calibration

If you use a probe, the process is usually quite simple: you connect the probe to the computer and place it flat on the screen (or facing the projector screen)3. A software provided with the probe (or the very powerful free software DisplayCal4) then performs a series of measurements of the colors displayed by the screen. The result of these measurements allows to calculate the shift between the displayed colors and the expected colors.

Screenshot of DisplayCAL Calibration parameters of DisplayCAL

If you calibrate by eye, the idea is to display a series of test cards, reference images, and try to adjust screen settings by hand to approximate the description of a reference image. It is completely impossible to correctly adjust the primaries* and the white point* by eye, but one can try to get close by displaying different images. On the other hand, the brightness*, the contrast*, the gama* can be relatively well approached thanks to comparisons of grey values between them (and a lot of patience).

To calibrate by eye several methods are possible, but everything always starts with the display of test patterns and reference images. Some operating systems offer them, but you can also find them on the net like the ones we propose here, carefully made to accompany this document.

These test cards can also be used to check the calibration result with a probe.

Black level

White level

White level

It is best to display these test patterns in full screen mode and with the environment controlled, as explained in chapter C.2 - Environment.

Then, by displaying the images, we retouch the screen settings. There are three possibilities:

It is not advisable to combine these different methods, as the result quickly becomes rather random, and especially difficult to retouch or correct afterwards.


At the time of writing, during our tests on Mac OS, the screen calibration tool in the system settings has a mediocre method (and results) (except perhaps on Mac screens) and does not offer test patterns worthy of the name, it should be avoided. It is better to calibrate directly with good test patterns such as the ones we propose, using the screen settings or other utilities.


Windows offers a good tool for calibrating screens by eye with rather good results. You can find it via the Control Panel, in Color Management then the Advanced tab. Then click on Screen calibration and let yourself be guided! It is in these options of Color Management that you can apply and choose the spaces and profiles (calibration result) of the screens.

Screenshot of Nvidia settings
Example of parameters via the settings of a Nvidia graphics card (under Linux). Note especially here the color range parameter, to be set to Full if the screen is a computer screen, and Limited if it is a television.

Screenshot of Nvidia settings
Example of parameters via the settings of a Nvidia graphics card (under Linux). Here, different sliders allow to adjust the display of the colors (for each screen). Each slider can act on the three channels* at the same time, or separately on the red, green or blue.

Mac profiling screenshot

Windows profiling screenshot

C.3.c.2 - Colorimetric profile

The result of the calibration of the probe, or sometimes of a calibration with the eye, is recorded in a colorimetric profile, a LUT*. It is the operating system which will apply this profile or this LUT to all the colors at the time of the posting on the corresponding screen and thus to convert these colors so that they are displayed exactly as they must.

Screenshot of Mac profile options

Screenshot of Windows profile options

Screenshot of Ubuntu profile options
Choice of color profiles under Ubuntu Linux in the Color section of the settings. A button allows you to add profiles (predefined or imported via a file, for example generated by a probe) to the list under each screen to easily change profile later.

Once the calibration is finished and the profile applied, you can check the result by displaying different test patterns (see above, C.3.c.1 - Calibration by eye), and also check the quality of the screen after calibration. Note that if you calibrate with a probe but the display of the test patterns is not perfect, it is probably more related to the quality of the screen than to a calibration defect.

Sources & References


  1. As long as the colors of the screen are more or less uniform and identical in the center as well as on the edges and in the corners… 

  2. It should be noted that it is not at all necessary for the screens to use the broadcast color space: thanks to color management, the displayed images are converted to the screen space so that the displayed colors are exactly those of the broadcast no matter what; calibrating the screens in the broadcast space just allows to avoid this conversion, and to avoid the common configuration errors by systematically choosing the broadcast space, whether for display, file output, etc.
    A concrete example: when working in video and for television, the images will be in Rec.709, but the working screens are by default in sRGB. When making the images, it is therefore necessary to specify (but this is often automatic), that the images are displayed in sRGB, whereas when exporting they will be chosen Rec.709.
    If we calibrate the screens in Rec.709, we can simply choose Rec.709 everywhere without making a mistake (but it is less standard in computing, and the default or automatic configurations may be wrong…). 

  3. It is advisable to start by restoring the screen settings to as neutral as possible, disabling power saving, the various modes (game, office, video …), to let the sensor and the system control the colors. 

  4. DisplayCAL is free and available on Linux, MacOS, Windows and supports a wide range of probe makes and models: https://displaycal.net/
    As always, we strongly encourage you to make a donation if you decide to use it!