Calibration of a printer : why and how ?
Published on April 15, 2015 / Updated on December 21, 2018

1 - Why calibrate your photo printer ?

A printer projects very fine droplets of Cyan, Magenta, Yellow and Black ink - CMYK - onto a sheet of paper with very specific characteristics. It must absorb the ink quickly but without diffusing it so as not to give the impression of drooling. Some printers allow you to choose the print resolution - spacing between droplets - which also influences calibration. Its calibration will teach us how it works.

The only way to know how the printer prints the colors is to ask it to print a reference file - a set of colored patches - whose colorimetric coordinates (CIE XYZ) and therefore the L*a*b* color perceived by a standard eye are known in advance and to read them with a spectrophotometer, sometimes replaced by a flatbed scanner, itself calibrated. The ICC profile builder software will only have to compare the printed CMYK values / L*a*b* colors to create the profile of this printer.

I would therefore like to briefly remind you of the importance of calibrating a printer: without calibration, a printer prints the colours with its own characteristics and therefore with defects. The quality of inks, paper etc. will greatly influence the way colours are printed. Even with the best printer, there is very little chance that a neutral CMYK signal - for example 51, 41, 41, 41, 8 - will produce a neutral grey on the printout. The generic ICC profile(s) sold with it will not change much, even if it has been an illusion since 2011, as there has also been significant progress in this area. But during this time, the calibration has also made the same progress ! Moreover, unlike screens, thanks to the image displayed on the screen, a comparison element is available. If the monitor is calibrated, it is easy to see if the print is correct or not.

The trap to avoid ! 

Obviously, in real life it is not all that simple because not all colour reproduction devices do it in the same way because of their technical limitations. In short : a printer may very well be able to reproduce a color that the display cannot show and vice-versa. In this case, you might think that your calibration did not work : "I don't have the same saturated yellow on my print as on my screen" or "My intense blue is not as dense on my print". Who to incriminate? Is my calibration really bad in these cases ? Well, we'll see that it's not that simple !

Important note ! When you evaluate your graphic chain once it has been fully calibrated, you must be able to read between the lines to understand why certain colors seem different between the screen and the printer and not automatically question its calibration, color management and hardware. You are then just at the limits of your equipment and the possibilities of calibration, even with the most expensive calibration equipment, especially because of the different gamut between your monitor and your paper !

However, it should be noted that the colorimetric space - the gamut - of the printers is so irregular that it often happens that towards a color, a given printer can print some out-of-range colors even for a large space like Adobe RGB ! We will therefore ask a printer to print an image close to the visual sensations we have experienced in front of a scene with infinitely fewer possibilities than in nature. It's quite a feat !

Be able to interpret any differences between a print run and its calibrated monitor

It is therefore very important to be able to correctly "read" the differences between the colors of a print and the colors displayed on the screen (even on a graphic chain calibrated around a wide gamut monitor).

The first tip is to take a good look at all the colors in a print with many different colors, more or less saturated and to be careful if ALL the colors seem really different from the colors displayed on the screen or ONLY CERTAIN. If only one or two colors seem correct but more or less saturated compared to the screen then you are on the right track and only within the color reproduction limits of your printer/paper system (due to a gamut difference).

Why can't we - and shouldn't we ! - calibrate a printer from a print run ?

For a very simple and important reason : the colorimetric defects of a printer, like any other color reproduction device, are never linear. What does that mean ? Quite simply that if you observe a slightly magenta dominant in your grays, this dominant will not be equal on ALL grayscales. You can very well observe a dominant magenta in the dark greys between levels 25 and 50 for example and rather green towards the very light greys. But then how can we correct these non-linear dominants? Well, with the color correction menu of your printer driver it is impossible because it only offers a precisely linear correction as shown in the figure below. If you move the magenta cursor to correct a green dominant, you will do so equally on all colors, all levels, of your photo.

Epson print driver for manual color correction when no ICC profile is used.

The only possible way would then be to edit a custom curve per color layer in Photoshop ! Laborious work if any and... automatically realized by a calibration kit and its spectrophotometer !!!!! Why bother then ?

There are two ways to calibrate your printer today...

Calibrating a printer with a dedicated kit is now within everyone's reach if they agree to pay the price: between £250 and $2,000. I personally use a lot the new i1 Studio kit £399 to calibrate my Epson 7800 printer.

Note ! The new £399 i1 Studio kit is based on the same spectrophotometer as the famous Colormunki Photo. So it's a "super" Colormunki Photo just a little more expensive.

Even without any particular know-how, you will obtain quality ICC profiles, much better than generic manufacturer profiles. That said, it must be admitted that generic profiles have also made great progress and that to print souvenir photos this will be clearly sufficient.

Now what if you are an amateur, professional photographer who values the quality of your prints ?

It can be said that in 2018, there are two approaches :

• Either create your own ICC profiles,
• or have them done remotely by a qualified service provider (paid or free).

Here are the advantages / disadvantages of both methods...

1 - Make your own ICC printing profiles :

a) Advantages 

• The pleasure of doing it yourself;
  
• You can easily create as many ICC profiles as you want, so with as many papers as you want,
• Whenever you want, even on Sundays!;
• We have a better understanding of what we are doing and what is happening : excellent from a pedagogical point of view;

b) Disadvantages

• The price : minimum £250/£400 and it can go up to £2,000 !
  
• Calibrating a printer is very simple but an expert can go even further with his own tools : this means that with the same calibration kit, a calibration expert who can create his own print patterns himself, will provide you with even better ICC profiles for your printer/paper pair, especially if you print in black and white, with your color inks.

2 - Have your ICC profiles printed remotely :

a) Advantages

• The price! you have no calibration kit to buy and the price of ICC profiles is on average under £50 (between £20 and £50). It is sometimes even offered by the brand of paper you use - Permajet papers -.
• For this price, you will also have a better profile - slightly - than if you had created it yourself; Why ? because some service providers like Christophe Métairie create their own charts to improve, for example, black and white calibration.
• Print with the best profile available !

b) Disadvantages 

• You don't have the pleasure of doing it yourself !
• You have to be patient and not want to calibrate your new paper on a Saturday night ! (Allow three working days as the printed test targets must be sent by mail. This does not happen by SMS!)