When Epson released their ABW system, we produced a test that would help show one of the significant differences between using six or seven shades of Piezography black ink in comparison to using only the three shades of Epson ABW. Epson enhances the perception of their black & white inkjet printing by adding dots of cyan, magenta and yellow ink to the three blacks. But, this does not increase the ability of three blacks to resolve resolution and detail.
We created a file of incredible resolution – the text of Alice in Wonderland reduced to 1pt size would replicate a high resolution photograph – but present something that is easier to understand and view in a side-by-side when magnified.
Alice in wonderland is replicated better by seven shades rather than three shades because of simple mathematics. The typical grayscale is comprised of 256 gray levels. Epson divides this into three inks. Piezography K7 curves are actually made of 256 divisions from more than 64,000 possible grays. Piezography K7 uses seven of these curves to print 256 gray levels. K6 uses six of these curves. The result of using Piezography is that it is much easier to print the gradations.
Another way of thinking about it is having 256 apples which three people have to carry (Epson ABW). Each person would need to carry nearly 86 apples which is quite an arm full. With Piezography the 256 apples are carried by seven persons, each holding only 37 apples – representing less than half the work. The Epson printer is good – but not that good when it comes to reproducing black & white with only three shades of black. Piezography K7 is excellent! K7 far exceeds the capability of the printer on which it is installed.
Speaking of apples – round and small like printer dots…a better way to understand why Piezography K7 prints with greater detail in the same printer that can not print at that same level of detail when used with Epson ABW – is to understand printer dots. Printer dots are comprised of ink droplets which are sprayed in a pattern according to the dithering requirements. Epson ABW has only three shades with which to replicate 256 gray levels. There are not enough shades in which to reproduce the lightest tones, so Epson relies on a dithering pattern that spreads the dots of ink apart. When the ink dots are spread wide apart, the human eye is fooled into seeing lighter tones. But, when the ink dots are spread apart like that, there is no ink with which to print fine detail.
Piezography K7 curves never print dots of ink spread apart. Instead, more dilutions of ink (shades) are used with which to carry the shades of gray that the Epson ABW dither cannot. Because the dots of ink are so close together when Piezography K7 is used, the detail which was not able to print with Epson ABW is clearly printed with K7. That is what you are seeing when you look at the Alice in Wonderland test above. K7 prints many more dots of ink per inch than can Epson ABW. The QuadTone RIP allows us to design a curve structure that prints dots of ink always touching and adjacent to each other. No paper white comes through that does not have one of the ink shades printing solid upon it.
We know some users who design their own curves with QuadTone RIP have not been able to reproduce our effect. The K7 curves are produced by our own software. Curve design and linearization is an art in itself.