Printers with mixed RGB and CMY inks??

GA
Posted By
George_Austin
Nov 15, 2006
Views
328
Replies
9
Status
Closed
Like the Canon iPK5000. It has 12 inks. Two C’s, two M’s, Y, R, G, B, two grays and two blacks. One of the great advantages of printing in CMY is that these inks can overlap without interference. Otherwise they would need to be in registration. How do printers such as the iPK5000 and iPK9000 integrate CMY and RGB colors, the latter of which cannot overlap even with each other?
Related Tags
ink print rgb

MacBook Pro 16” Mockups 🔥

– in 4 materials (clay versions included)

– 12 scenes

– 48 MacBook Pro 16″ mockups

– 6000 x 4500 px

JS
John_Slate
Nov 15, 2006
I’m not following you.

What do you mean by "…these inks can overlap without interference. Otherwise they would need to be in registration."?

I don’t know the printer but I would guess that it would not print large amounts of R on G or B, but rather print some amount of R only in saturated Red areas, some amount of G only in saturated Green areas, and some amount of B only in saturated Blue areas.

Printing a lot of red on green or blue would, as you surmise, produce mud.

If by "interference" you mean moire from dot angles, that would not happen with FM screening, and registration is pretty much not an issue for inkjets.
GA
George_Austin
Nov 15, 2006
John,

I’m referring to printer dots dithered (scattered) within a pixel. CMY inks function just as well wherever they fall within the pixel boundary. C MUST not overlap C, nor M overlap M nor Y overlap Y. But C MAY overlap M or Y, M may overlap C or Y, and Y may overlap C or M. There is a preferred order of overlap, because there is some secondary interference. At printer resolutions, the eye cannot discern the dot arrangement and "sees" only the net effect. If you look at the printed result with a magnifier, you WILL see the arangement and it will be chaos.

"…I don’t know the printer but I would guess that it would not print large amounts of R on G or B, but rather print some amount of R only in saturated Red areas, some amount of G only in saturated Green areas, and some amount of B only in saturated Blue areas…"

If the printer husbanded the R G B inks as you suggest, those ink cartridges would be used so sparingly they would not carry their weight. But that’s what my question is about…How are CMY and RGB inks integrated in such printers?

George
KV
Klaas Visser
Nov 15, 2006
But that’s what my question is about…How are CMY and RGB inks integrated in such printers?

In my opinion, they are integrated by the printer driver, and printer mechanics, to provide a larger gamut than is otherwise usually available in an inkjet.

I’d also suggest that this ink blending is transparent to the user. They just create an image, send it to the printer in the usual way, and it (driver/printer) works out what inks need to be used. I don’t think it seperates CMYK usage from RGB usage.

Reading the spec sheet, it indicates that the printer uses GARO technology, so I think this bears out my suggestion.
GA
George_Austin
Nov 15, 2006
GARO technology? Hmmm—I’ll look it up.

Contrary to the popular cliche, one has to think INSIDE the box here. What is happening within the confines of a single pixel? Just mulling it over with others stimulates the brain (what’s left of it).

It’s dawning on me now that C, M, Y nozzles may be fired at a single pixel site, but the other inks must not be mixed at any site. Further, the two shades of Cyan would not be fired at the same pixel site, nor the two shades of Magenta, the two shades of gray, and the two shades of black. I guess R,G, and B would also be used individually as well.
GH
Gernot_Hoffmann
Nov 15, 2006
George,

without knowing your printer – one has to
imagine inks as thin filter layers on the
reflective paper, thickness about 1 micrometer.
Each layer absorbs its complementary color:
Cyan absorbs Red.
Magenta absorbs Green, an so on.

Red can be made by adjacent (or overlapping)
spots of Magenta and Yellow:
Magenta absorbs Green.
Yellow absorbs Blue.
White light with absorbed Green and Blue is Red.

This is probably not a ‘pure’ or ‘clean’ Red.
If we had an ink which absorbs Cyan, then the
reflected light would be Red as well, and hope-
fully a ‘cleaner’ Red.
That’s IMO the reason for using additional inks.
It’s not ‘RGB thinking’. The color mixing model
is still subtractive, concerning the filter layers
(and additive for mixing the reflected light by
eye+brain).
The choice whether Red is printed by M+Y or R ink
is up to the printer driver designer – no unique
solution (but we know this ambiguity already –
a certain amount of CMY can be replaced by K).
The reflectance factors for CMY inks are really
far from being ideal, this is shown here in
chapter 9:
<http://www.fho-emden.de/~hoffmann/prooflight18092003.pdf>

Light Magenta and Light Cyan is used for improving
the spacial distribution: more spots per area of LM
instead few spots for (normal) M.

Best regards –Gernot Hoffmann
JS
John_Slate
Nov 15, 2006
as far as thinking inside the box (pixel): once the image is screened (FM or AM) there is no more box
DM
Don_McCahill
Nov 15, 2006
You might find This article < http://www.pantone.com/downloads/articles/pdfs/hex_print_pro cess.pdf> of interest. It describes the Hexachrome system used by commerical printers to generate richer colors than CMYK. It will not be the same as your home printer, but the theory is related.
MD
Michael_D_Sullivan
Nov 16, 2006
GARO technology is Canon’s name for its printer control language — Graphic Arts language with Raster Operations. It sounds like it may be a Postscript substitute that avoids paying license fees to Adobe.
GA
George_Austin
Nov 16, 2006
Gernot,

Thanks for elaborating. I could not have said it any better.

George

How to Improve Photoshop Performance

Learn how to optimize Photoshop for maximum speed, troubleshoot common issues, and keep your projects organized so that you can work faster than ever before!

Related Discussion Topics

Nice and short text about related topics in discussion sections