U of S | Mailing List Archive | alt-photo-process-l | Re: Custom color-separations in Photoshop?

Re: Custom color-separations in Photoshop?

Funny, after reflecting on this for a while I was just coming back to say roughly the same thing Michael just said, that I think there's still something in the idea of spot channels. I'm trying to remember the name of the person (on this list, I think) who showed us color gum prints made by creating his own separations, which if I remember right were essentially spot color channels created by selecting colors with the magic wand. I'm just remembering this vaguely, but I think this guy's work may have been in the direction you're thinking, Keith. The images were European city scenes, as I recall, maybe Venice. If the person is here I hope he'll speak up, or if someone else remembers who this was and has the link for the pictures/ instructions, please chime in, thanks.

On Jan 24, 2009, at 4:32 PM, Michael Koch-Schulte wrote:

No. I think you're on the right track. Damn the "experts". There is a reason "spot" colour exists to this day and people in the printing industry know why. There are colours which can't be produce by just three "primaries" and there are also cases when primary colours are both not necessary and to be avoided. For example, mixing quinacridone red and azo yellow will give you "an" orange but it won't be as saturated or intense as say a benzimida or pyrrole orange which are both produced independently of either red or yellow pigments. Many fine art reproductions use multiple plates. Giclee uses 12 inks not 3.

Keith Gerling wrote:

Forget it. After some reflection and after mulling it over with a
resident PS expert (thanks Mark), it is apparent that what I'm looking
for is impossible. There is a reason they are called Primary Colors!

I will check out the Hexachrome thread, though.

On Sat, Jan 24, 2009 at 12:22 PM, Katharine Thayer <kthayer@pacifier.com> wrote:

Spot color separations?

No, on re-reading, I think you're talking about something more
sophisticated. In a fairly recent thread, someone pointed to software (not
Photoshop) that provides separations for two of the secondaries, I think, in
addition to the primaries, but I didn't see anything that generates
separations for all three. But that thread might be a good one to revisit.

Ah, I found it. The thread subject is "Gum Color Gamut & Beyond CMYK"
starting September 22, 2008. On re-reading, I'm not sure it contains much
useful information beyond the name of the application (Pantone Hexachrome)
that makes the five-color separations. But you might read through to see
for yourself.


On Jan 24, 2009, at 9:49 AM, Keith Gerling wrote:

I was wondering if there was any method in Photoshop, or with a
Photoshop plugin where one could perform custom color separations.
The RGB and CMYK channels are universal ways of splitting a full color
image into 3 or four standard colors. Wouldn't it be possible to
split an image into components of Purple, Orange and Green, for
instance? It would be like turning the color wheel a notch.
Conceivably, if all the color information can be conveyed in CMYK, it
ought to be accurately conveyed with other color channels as well.
Or am I missing something?

This could provide all kinds of interesting possibilities for
tri-color gum printing.