‘How can I print true gray by my common inkjet printer?’
In short: Sorry, it is impossible. You can just counterfeit. Not genuine gray as you wish. Zygomatic Color is the best ICC profile builder for the job.
In long: It is a long long story.
Three primary colors… Is it true?
Have you ever tried to make achromatic color by mixing color paints? It should be possible if the ‘three primary colors’ theory is true. But you failed, right? You can make very dark color, but it is not achromatic.
You can make green by mixing yellow and azure. This makes sense. You can make the green darker by adding violet. The ‘three primary colors’ theory is true for most cases.
Theories have exceptions. Aristotelian dynamics is true except for scientists. Newtonian dynamics is true except for extremely fast objects. The ‘three primary colors’ theory is true except for gray objects.
Do you have a genuine gray card for photo?
If you are a photographer, you will surely have a genuine gray card. You might have seen poor fake gray cards on Amazon.com or eBay. Such fake gray cards are absolutely blue-ish, green-ish, or red-ish, just like when you tried to make achromatic color by mixing color paints. Poor fake gray cards are made by common inkjet color printers. A common inkjet color printer prints gray by mixing CMY. The phenomenon is the same.
Every color displays work by RGB emitters. But we don’t feel a display’s gray like poor fake gray cards, as far as the white balance is perfectly adjusted.
A genuine gray object is something special. The ‘three primary colors’ theory is not true for a gray object, and only for it.
A gray object is a special thing
There are several reasons for the phenomenon.
- Illuminant dependency. In other words, a fake gray card can be true gray under a particular illuminant. A genuine gray card is always true gray under any illuminants.
- Our eyes are especially sensitive to colors around gray.
Illuminant dependency explains why a color display can show true gray by RGB emitters. A color display itself is illuminant. But an object reflects light from illuminant.
Illuminant dependency is a very common phenomenon. But our eyes rarely find it, because they are insensitive for the subtle tone of saturated colors. Besides, paint / dye manufacturers do their best job to reduce the phenomenon. Our eyes are exceptionally strict for gray. Besides, paint / dye manufacturers are clever enough to say ‘Buy black and dilute it by white, instead of mixing CMY.’ Of course, printer manufacturers are clever enough to say ‘Buy an expensive photo printer.’ The problem is unique to common inkjet color printers’ gray.
Illuminant dependency is a phenomenon which comes from the spectral world. In the world, light isn’t RGB. RGB is discrete like a histogram. Spectrum is continuous like a curve chart. The ‘three primary colors’ theory cannot play well in the spectral world.
Yellow colorant absorps short wavelength (blue) and reflects other wavelength. Cyan colorant absorps long wavelength (red) and reflects other wavelength. In this way, every colorants have bumpy spectral reflectance curve.
Genuine gray has flat spectral reflectance curve. Fake gray is made by mixing CMY. How can we make a flat thing by mixing bumpy things? If the problem is in the RGB world, it is possible. In the spectral world, it is impossible. Bumpy fake gray is the fate.
Sorry, no help. No one can make genuine gray by mixing CMY.
My first advice: Buy an expensive photo printer which have gray and light gray inks.
Better fake gray?
Let’s counterfeit a gray object. In other words, let’s adjust gray balance.
Every colorants have bumpy spectral reflectance curve. The curve varies depending on the manufacturer and the product line. Our eyes say ‘cyan is cyan,’ but it isn’t true in the spectral world. A poor quality ink set lacks a few hidden virtues. Illuminant dependency is one of them.
My second advice: Use a high quality ink set.
But the evaluation of illuminant dependency is a problem. Your eyes are not suitable for the job. You need to try to make true gray by adjusting CMY until you say ‘OK, it is true gray, absolutely true’ under a specific illuminant, and go under other illuminants. If you do it just by yourself, it’s too hard job.
Zygomatic Color is the best ICC profile builder to counterfeit a gray object. Dye sublimation is notorious for bad gray balance. Sublinova ink has a good reputation, but the untuned gray balance is astonishingly bad. Zygomatic Color is made to tame incorrigible ink sets like this.
To Sublinova’s reputation, the illuminant dependency is very good. Look at the Lenin’s face below. When tuned by Zygomatic Color, Sublinova’s gray is very true under CCFL (my scanner EPSON Perfection V600) and xenon flash both. A poor quality ink set cannot play like this.
Unless you find out a high quality ink set, you don’t need to pay for Zygomatic Color service. Zygomatic Color evaluation PDF contains several gray charts. You just print the charts, and just try next ink set if the result is not enough for your eyes.