Shouldn't we be having this discussion on Inkjet_PCB_Construction?
Yes, all printers use CMYK or an expanded version. The most common are a light version of Cyan and Magenta, sometimes a "photo" black that may be a grey. They are usually indicated by lower-case letters such as CcMyYKk. Some expensive printers have additional colors, green and orange as they can be very hard colors to hit correctly. Some printers have additional shades of grey. These are all to avoid the appearance of visible ink dots in light and evenly colored areas, widen the color gamut (range of shades printable), and to avoid color and texture shifts.
RGB only works for additive things like monitors. CMYK is subtractive. Add 100% Red, Green, and Blue on a screen and you get white, add the maximum Cyan, Magenta, Yellow, and Black and you get Black. Try mixing paints in Red, Green, and Blue, and you'll find there are many shades you can never get. Green and Blue only add to yellow if you are mixing light. Mix inks or paints, Green and Blue become a muddy dark green-blue color.
The confusion likely stems from the fact that the printer driver for desktop printers only accepts files in RGB color space, then converts them to the printer ink color space. CMYK, CcMmYKk, etc.
Separations won't help you - the separation, if printed on your home printer, will still be just an image file that will be printed as if it were an RGB color space file in black, which gets converted by the printer drive to the printer CMYK color space.
Using CMYK within Photoshop can help a little, but ultimately all files printed first get converted to RGB before getting sent to the printer driver.
What you really need is a RIP, but those tend to be expensive. There is Turboprint Studio, which I've not used since I had it on my Amiga 3000, but there is a version for Linux. The Amiga version of TurboPrint Studio 2 let you control every ink, so you could set it to print only in one particular ink.
http://www.turboprint.info/I see the programmer has a version for Windows and Mac called PrintFab. Appears to still be in beta testing.
http://www.printfab.com/en/You could also find a color in RGB that prints mostly magenta and/or cyan.
BTW, the C82 is not a "photo" printer in the meaning of having the lighter color inks such as photo cyan and photo magenta. It is a four color CMYK printer. Still, the printer driver only accepts RGB image files and does the conversion to the printer's CMYK inkset.
Steve Greenfield AE7HD
--- In Homebrew_PCBs@yahoogroups.com, lists <Stuartlists@...> wrote:
>
> In article
> <CAFgkapC58p0cp9Sik=AXAUPJx8=omhKzvTbz6rzQ1JZZzHmjDA@...>,
> Andrew Thornber <andrew.thornber@...> wrote:
>
> > Personally if you need to print CMYK then have a look at photo printers
> > as they print in the CMYK space. (It's oldish but to prove a point have
> > a look at the Epson C82)
>
> I think you will find that all printers, including "home" printers use
> CMYK. Certainly all the ink-jets I have owned did. The difference with the
> "photo" printers was that they used two further inks, paler versions of
> cyan and magenta usually, in order to achieve the delicacy of colour.
>
> One rather old piece of DTP software I have could produce the required
> CMYK separations as separate files on a disc for submission to a
> commercial printer. I guess it would have been possible just to print
> locally from one of these separations.
>
> Although of necessity it uses RGB to display stuff, Photoshop can use a
> variety of "colour spaces" internally but I'm not enough of an expert to
> know whether it can print the separate colours to a printer.
>
> However, photoshop is just a teeny bit expensive!
>
> --
> Stuart Winsor
>