Re: Gum Color Gamut & Beyond CMYK?
Yes I understand what you're saying. I just thought it illustrated a method of 'fine tuning' the image using 6 pigments rather than the 3 or 4 that most people use (for tri-colour work) and sort of fitted in with your discussion. It does seem rather a lot of work. I wonder why the man on flickr decided on this route rather than research his pigments? Maybe he did..
On Sep 21 2008, Katharine Thayer wrote:
Just a clarification: since this was a response to my post rather
than to Jacek's or Loris's, I should perhaps emphasize that this
isn't exactly what I (per Bruce McEvoy) am talking about on my
tricolor page. What McEvoy means by using six colors to produce the
secondaries and tertiaries accurately is the three primaries plus the
three secondaries. What the fellow on flickr, and Jacek, mean by a
six-color process is CMYK plus two secondaries. Not the same thing.
On Sep 20, 2008, at 11:16 PM, email@example.com wrote:
> Take a look at this photostream in flickr
> It's exaccerlly what you're talking about
> David H
> On Sep 21 2008, Katharine Thayer wrote:
> See my page on tricolor gum printing
> for a brief consideration of this topic (scroll down the page to the
> subheading, "Is it possible to reproduce the entire spectrum using
> three color layers?" )
> The answer, from Bruce McEvoy, is no, you do need to add the
> secondary colors (in other words, in gum printing, use six layers
> including the secondary colors in addition to the primary colors, in
> order to produce accurate colors throughout the spectrum, and I
> suppose some sort of profiles as Jacek suggests might be the way to
> generate the color separations for the secondary colors. But this
> seems to me an enormous effort and possibly a misplaced effort to
> boot; if you're looking for this kind of color precision, gum may not
> be the right process for you. Not that I would discourage anyone
> from dedicating themselves to this kind of study if it appeals to
> them, just that for me and my house, I don't quite see the point.
> However, the purpose of the extra colors and separations, as I
> understand it, is not to extend the gamut so much as to refine it.
> Depending on the pigments you choose as primaries, the layered color
> mixtures will produce different palettes of greens, oranges and
> purples; generally when printing tricolor we pick three primaries
> that give us the kind of secondary mixtures we want. For example, I
> generally prefer ultramarine or prussian blue for tricolor because I
> don't like the greens that pthalo produces with almost any yellow,
> they look unnatural to me, and since I print a lot of landscapes with
> trees/leaves, I want a more natural looking palette in the greens.
> Adding the secondary colors to produce six layers will theoretically
> make it less necessary to pick and choose primary pigments to produce
> the kind of secondaries you want, because you can choose the
> secondaries to your liking. But like I said, this seems a heck of a
> lot of work, when three colors, chosen carefully, will almost always
> give us a palette that gives us a reasonable enough approximation of
> realistic color, with special attention to producing the secondaries
> that we're most interested in.
> On Sep 20, 2008, at 9:11 PM, Jacek Gonsalves wrote:
> > Hi all,
> > Just continuing what Loris was talking about in regards with using
> > a predefined set of pigments and building a profile for Gum
> > printing. If one could build the profiles based on the CMYK
> > pigments, can we say that this holds a certain color gamut. Lets
> > say we want to increase the color gamut?
> > There are other methods as Pantone Hexachrome method of 6 color
> > separations CMYKOG, adds orange and green separation. Adding these
> > additional separation would therefore increase the color gamut.
> > That is if the image you have includes those additional colors.
> > I'm sure there are methods to make additional separations in PS,
> > though it might be complicated? If someone knows how to do this
> > please chime in..
> > Though it excites me to think that one could increase the color
> > gamut from finding what pigments fall further than the usual inkjet
> > printers do these days.
> > Regards
> > Jacek