Re: How does the printer choose which black ink to use when it has pigment and dye based black ??

Tony wrote:
Michael Johnson <cds@xxxxxxxxx> wrote:
Tony wrote:
Michael Johnson <cds@xxxxxxxxx> wrote:
Bob Headrick wrote:
"Michael Johnson" <cds@xxxxxxxxx> wrote in message news:yYqdnUbML8ZYrQPanZ2dnUVZ_u-unZ2d@xxxxxxxxxxxxxxx

I just performed the tests that Dan mentioned and they do show that pigment black is used when printing color on plain paper. When I specified photo paper the black lead-in ink wasn't present and it looked like all the colors (including black) were laid on the page during one pass of the head. Because of the configuration of the nozzles, this would only be possible if it used only the dye black cartridge.
The last statement is just not true. Printers can and do lay down drops from black and color in the same swath, even if the black drops are larger and contained in a different printhead with a different swath size. This happens to be the absolute truth, you can doubt it if you wish but I have said all I care to on the subject.
All the nozzles used put ink on the page in a given swath but in the Canon printers using pigment and dye black, on plain paper, the color is laid down on the pigment black in subsequent passes of the head.
I seriously doubt this is true, it flies on the face of my understanding of the way ink printers work. It also would not be smart design as the industry competes for speed as well as quality.
Until I did the tests with the MP780 this afternoon I would have said the same thing. Look at a head from this printer and you will see that it is more than possible. Canceling the print command in the middle of printing a color picture on plain paper shows a clear black only pass(es) followed with the color inks supplied on later passes. The only way this can occur is for the pigment nozzles to lay the pigment ink down in a previous pass of the print head before the color nozzles reach this point on the page. It is physically impossible for it to happen any other way.

Well, you and Art have fired my interest. I will see if I can do some investigation of my own, it is quite an intriguing matter albeit probably of little practical importance. Maybe I'm hooked, I will come back here if I discover anything of note.
Thanks

Maybe the print heads on other printers are different but I suspect any printer using both the BCI-3 and BCI-6 black tanks operate the same way.
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