Re: Gum Color Gamut & Beyond CMYK?
Thanks, David; it's interesting to know that someone has actually tried this, and with the Hexachrome separations as Jacek suggested. But........I don't find the print particularly compelling as an argument for going down this path. Three layers could do as well, or better in the hands of a skilled printer, both from the standpoint of representing that particular palette well, and the standpoint of tonality. He notes that it was the "death of the greens" in a previous print, the fern print, that caused him to explore 6-color printing, but it's not three color (or four color in his case) printing per se that gives it those dull ooky greens, it's the choice of pigments and pigment concentrations. A better, and easier, solution IMO would be to choose a better pigment combination and work on his tricolor printing skills. But, each to his own. Katharine On Sep 20, 2008, at 11:16 PM, davidhatton@totalise.co.uk wrote: Hi, Take a look at this photostream in flickr http://www.flickr.com/photos/herbhoover/422834327/ It's exaccerlly what you're talking about Regards David H On Sep 21 2008, Katharine Thayer wrote: See my page on tricolor gum printing http://www.pacifier.com/~kthayer/html/tricolor.html 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. Katharine 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 > > > >
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