I'm moving this thread away from the Luminous landscape forum b/c I don't want any misinformation I have to serve as ammo for the naysayers.
Walker, you posted "4 shades is not as good as 7 (although much better than 3). Dual K4 is much closer to 7 than single K4 and much better than 3".
All I can say is Wow! I asked that same question as the OP about more shades being better than fewer shades years ago (when 4 ink PiezoBW was the standard and Epson released 6-ink printers) and very recently before investing $1500 in a dedicated desktop b&w printing system. Walker, I got the same information both times.
So it appears I may have based my PiezoPro purchase on bad info. Your claim is the more shades of gray, the better the print quality in terms of tonal resolution and detail resolution; and my conclusion that it's the software that equally generates a seamless tonal range whether using 4, 6, or 7 shades is faulty as well.
I understand you to claim that the K4 PiezoPro inks, although producing a better print than the K3 Epson ABW, do not equal the Piezo K7 inks you currently offer? Following this same "the-more-shades-the-better the-print" reasoning, all other factors being equal, would not the 11-ink printers produce even better quality prints than the 9 -ink or 7-ink?
With PiezoPro, I had the understanding that I could produce cool, neutral, or warm shadows, mid tones, and highlights or any combination thereof in a stepless density range from 0-100%. In what way is the K7 Piezo superior to the quality of the PiezoPro?
Also, Your claim that PiezoPro "dual K4 is better than single K4", implies that there is an ideal blend of warm and cool for the " best" image quality. How do I determine that mix?