[cairo] Spot colors (and CMYK)

[ecir hana]

On Sat, Feb 20, 2010 at 9:28 PM, Chris Murphy <lists at colorremedies.com> wrote:
>
> I do not follow the logic on this at all.

It's very simple: sometimes you just don't have a profile.

I asked you several times, where should I get a profile for Pantone
duotone. Or glossy varnish. If it was mandatory to always supply a
profile, what should I do?

> An XYZ or LAB alternative for a spot color is an obviously good idea if you want to see the spot color on any kind of device that does not print with the exact spot color (ink in a bucket). Depending on how the spot channel is used, determines how it would be defined.

> If it's just for a logo or something like that, an ICC profile for the spot color isn't necessary, just an XYZ or LAB value so it can be displayed and proofed properly.

LAB fallback = tagged CMYK fallback, that's what I said.

> If you insist on untagged device values, you can only use spots except where ink in a bucket is present. Bad idea.
>
> Wrong. You want a particular result, and specifying it as 100K isn't going to get you there because some downline process *will* convert it the instance K100 isn't available. It's important to define the object type. Black text is unique and needs variable handling. Simply saying it's always 100% K can result in incorrect handling.

How do you know what I want? I want one solid plate. Don't care where.
"The correct answer is, it depends.", as you said to Bill Spitzak.

>> That said, I understand that untagged CMYK is difficult to show on the
>> screen. I'm not against tagged content - I'm against making tagging
>> mandatory for spots. Perhaps always tagged CMYK is even a good thing
>> but for DeviceN that means only its fallback. (And I could always
>> create untagged DeviceN with cyan, magenta, yellow and black). I also
>> believe DeviceN should have its fallback defined in CMYK only, and the
>> fallback should compose over CMYK only, as well).
>
> This makes zero sense to me.

That's PDF/X-1a. There is just one tagged CMYK for everything, except
for spot colors (but their fallback is in that CMYK, too)