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Calibrating a screen with a colorimeter


Why calibrate your monitor?

Published on April 15, 2015   |  Updated on October 31, 2019


Simply because it is essential ! And why is that ? Because it is the starting point for the work on your images, because you want them to be as good as possible and because your eyes are unable to help you faithfully in this task. Did I convince you ?

At least get yourself this gift: calibrate your screen with a monitor calibration tool. You have no idea how much this will change the way you work! At the prices they cost today, it is no longer possible not to buy one !

Absolutely ESSENTIAL for those who work with computer images, screen calibration unfortunately cannot be done efficiently without a calibration tool sold with its ICC profile creation software. Prices have dropped significantly like the entry-level colorimeters Spyder5Express (Datacolor - Which I recommend since this fifth version) or Colormunki Smile (X-Rite - Which I don't recommend) cost $81 now and the so-called "Pro" versions cost only slightly more, about $130; it's an excellent price/quality ratio. The references today that are the  i1Display Pro from X-Rite or SpyderX Elite from Datacolor cost between $200 and $280 including VAT. It really doesn't seem very expensive to me in terms of the cost of digital photography equipment and the sums, sometimes significant, that are swallowed up in ink and paper cartridges or computers, for the services provided .

The calibration of a screen is actually done in two steps :

  • The calibration itself,
  • Characterization then ?

It is only in this second step that the ICC profile of the display (device characteristics) is created. First, I will explain these two terms. Even if I will insist on calibration with a calibration tool, in the second part I will explain why it is not only essential but also very different to calibrate your screen with the naked eye or with a print. Then, on the next page, I will discuss the question of how and on the third page I will review almost every Colorimeters on the market and I'll end up with a summary page where I give my advice on buying colorimeters by equipment category : laptop, iMac, iPad, classic desktop, Graphic Art.





The problem of calibration ?

Calibrating a screen consists of making three VERY IMPORTANT settings and... an important choice !

  • On the one hand, to neutralize the dominant colors, thus the defects of the screen display,
  • and on the other hand, adjust the screen so that it displays a good level of brightness and a good contrast,
  • ensure that it displays the widest possible range of colours,
  • and finally make the right choice of screen technology !

Under no circumstances can these adjustments be made with the naked eye because the eye, if it is an excellent comparator, is very bad in absolute terms.

1 - Correct the dominant colors and optimize the color range

Écran calibré / non calibréAs we have seen on the pages devoted to the introduction to color management, all color reproduction devices reproduce them with their own deformations. We would like the screen to display a neutral grey and it displays a grey with a dominant, not to mention the defects of the printer, etc. Calibration will consist in sending to the screen a series of RGB signals whose absolute color is known precisely (i.e. the XYZ values in the CIE XYZ or L*a*b* space in the L*a*b* space) and measuring with a calibration tool - a colorimeter - how it actually displays them. To take an example : if I send an RGB signal of type 128, 128, 128 to an uncalibrated screen, there is very little chance that it will display a perfectly neutral grey (although there has been progress since 2012). It is very likely that it will display a grey with a slight dominant color (reddish, greenish etc.). The colorimeter will measure this "true" color displayed (therefore its L*a*b* value) and place the information in a small special file : the ICC profile of this screen. With this ICC profile created in this way, Photoshop, for example, will know which R'B'V' corrected RGB signal to send to this screen so that it displays the right L*a*b* color, here a really neutral grey. When I want to display this neutral grey on this screen, from now on, the graphics card will have to send it a signal of the kind - 124, 128, 128 - to take into account its characteristic (its defects), which is in this case a defect in the reds. By doing all this, the screen will display the widest possible range of colors, especially since you will finely adjust the next step using the same colorimeter.

2 - Adjust the brightness of the screen

Adjusting brightness on an iMacAnother often overlooked point is the adjustment of the screen brightness so that the brightness of the picture on the screen is close to that of the printed picture. This adjustment cannot be done, as for the correction of the dominant colors, with the naked eye and therefore requires a calibration tool that will precisely measure the true level of brightness of the screen according to the instructions you have given to the software. This is the calibration phase.

3 - Adjust the screen contrast

A last point that is often overlooked is the adjustment of the screen contrast. The contrast setting is used to adjust the darkest black level on your screen. This can therefore be a real problem for the calibration of laptop monitors that never have this setting. The colorimeter should therefore automatically take care of it... normally !

My advice !  If you work mainly for the Internet, always choose: "Native contrast". On the other hand, if you print regularly or are looking for a good screen/sorting match, choose "Contrast 287:1" when possible.

4 - Are all screens equal ?

I invite you to read this page where I give you some buying advice, my opinion on the selection criteria (especially screen technologies for photographers) and my vision...

All my advice to choose your photo editing screen    

Let's now look at the two steps of screen calibration: calibration and characterization, thus the recording of its precise colorimetric characteristics.



Calibration and characterization

As has been mentioned several times now, the calibration process is actually a two-step process : a calibration and then a characterization (with exceptions such as the iPad).

Calibration of the screen

Screen settingsTo ensure that the color reproduction device that is a display operates under optimal conditions, it must first be calibrated, which means that its basic operation must be optimized and placed under known and, if possible, stable working conditions. With the screen, the tool of the graphic chain that concerns us on this page, calibration is used to fix once and for all :

  • The maximum brightness - white point - of the screen;
  • The contrast;
  • The gamma;
  • The color temperature - in Kelvins -;
  • And possibly the minimum brightness - the black point -.

This operation, called calibration, can be done in two different ways depending on the quality of the screen you have purchased, but always using the colorimeter :

  • With a screen that is qualified as not "art-graphic", i. e. almost all screens, this is done using the Menu keys and the colorimeter that is used during this calibration step as a calibration tool. A series of colored thumbnails appears on the screen to allow this calibration. One of the most important points is whether the software offers the possibility to precisely control the amount of light it must emit, at the maximum and minimum. This should ideally be close to 80/140 candelas per m², depending on the lighting environment in which you work so that the brightness of your print is very close to the brightness of your photo on your screen. This can only be done with a measuring device. The human eye is absolutely incapable of doing so without any element of comparison.
  • With an "art-graphic" screen, it is enough to set these four target values in a menu of the software and to simply launch the calibration which is then done automatically (the characterization is done in the process).

Note that once the screen has been characterized - i. e. profiled - these settings should not be altered ! Otherwise, the characterization would have to be redone, thus recreating another ICC profile for these new calibration conditions.

The characterization

It is during this second step that the ICC profile of the display is actually created, taking into account the settings that were optimized in the previous step, i.e. during calibration. We will now measure the color characteristics of the monitor placed in "ideal" operating conditions or at least known and precise (ideal means that we would then no longer need to profile the screen). The calibration software then sends a series of RGB signals to the screen and the actual colors displayed are analyzed and compared to the ideal colors - L*a*b* - of the ICC Consortium using the screen colorimeter - a colorimeter shown opposite.

Attention ! If you characterize with your eye you will only make a comparison and not a measurement. This step is therefore impossible with free calibration software based on the comparison of colored patches. The software therefore produces the colorimetric identity card of the device by measuring :

  • The colorimetric space that it is able to reproduce in relation to the L*a*b* space ("gamut"); it is the result of the black and white dot on this screen and the maximum saturation of the filters placed in front of each pixel on your screen;
  • And how it reproduces it - which RGB signal for which L*a*b* color.

Very important ! All distortions of the colors displayed on the screen in relation to the L*a*b* colors will be carefully noted in this special file, the ICC profile of this screen. When the graphics card wants to display this or that L*a*b* color, it will know exactly what "corrected" RGB signal to send it so that it displays them correctly, taking into account its famous characteristics. An ICC file can therefore be a rather large file because it can contain an impressive amount of information. The colours that a screen can display are indeed very numerous - a very good eye can distinguish, I would remind you, nearly 8 million colours! With the eye, this adjustment can only be approximate, even if it sometimes creates an illusion because the gamut of a screen is not very wide - even if it increases with new neon or LED technologies. While it is still often close to the sRGB color space, more and more screens can now display the Adobe RGB space, which is significantly larger or even larger, which justifies that the calibration equipment is changing quite a bit at the moment. Many photographers put up with the initial problems with the first LED screens, perfectly mastered today (summer 2018).

On the next page, we will study how to calibrate the monitor? - 2 / 5  Suivre


To be remembered !

Calibrating the display with a good calibration tool is essential and now perfectly affordable.

 Do not buy the first price colorimeters (Spyder3 or 4Express or Colormunki Smile) really not very recommendable - But with a notable and recent exception, the Spyder5Express which is finally recommendable - and hardly less expensive than the Pro or Elite versions, which are very efficient.

The name Pro or Elite is misleading : there are no amateur colorimeters and pro colorimeters; there are those that work very well, whatever the screen, and those that are so simple that calibration is often bad and random. They are therefore difficult to recommend. So "even" amateurs must buy the "Pro" versions !

Calibrate between 80 and 100 Cd/m² if you are working on images for printing (and if you are in a dimly lit environment, use higher levels) and work at 120/140 Cd/m² if you are working on images mainly for the Internet.

Through these 6 pages of advice and my 12 full colorimeter reviews I will help you to properly calibrate your desktop or laptop screens, your iMac or your tablets...
- Why calibrate your monitor ? - 1/6
  - The problem of calibration
- Calibration and characterization ?

- How to calibrate your monitor ?
- Special case : iMac / iMac Pro calibration
- Special case : calibrating laptops
- Special case : calibrating tablets and smartphones
- Special case : Eizo ColorEdge + ColorNavigator


- Best colorimeters buying guide
- My monitors buying guide 2020


Calibrate your monitor with the best
colorimeter: X-Rite i1Display Pro !

Read my full review...


Calibrate your monitor with your favorite colorimeter : Datacolor SpyderX PRO !

Read my full review...










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