[CREATE] Color swatches

[Louis Desjardins]

I just realised I sent my answer only to Kai-Uwe and not to the Create list.
Here it is. Sorry Kai-Uwe for double-posting.

2008/4/7, Louis Desjardins <louis.desjardins at gmail.com>:
2008/4/7, Kai-Uwe Behrmann <ku.b at gmx.de>:
>
> Am 06.04.08, 17:16 +0200 schrieb Olivier BERTEN:
>
>
> > Now some thoughts about color swatches in general and about the CREATE
> draft:
> >
> >
> > Registration color
>
>
> What does Registration mean?


Registration is the color that will appear on each and every plate of a
printed document, in the mean of a "Registration Mark" (a target like small
mark, usually made of circle with a cross) and that will also appear on the
printed sheet as crop marks. These marks are there to help the printer
(human) to fit the plates perfectly on press.

So, no matter what color is used in the end document and how many are they,
the Registration color is actually composed of them all, at 100% each.

Registration color can (or should) only be used for those marks.
Registration color is not really a color per se in terms of plates. It does
not create a plate of its own. Each of its components appear on the various
plates of the document. Usually, the user doesn't have to pick this color if
the program can produce the registration marks my itself. But if a user
wants to create one's own marks or for various reasons create a document
with the marks appearing on the actual page inside the boundary of the
document, then it is useful to have access to this "color" in order to be
able to apply it to such marks.

> IMHO, this shouldn't come in a color swatch file. It's a "system" color,
> just
> > the opposite of 'None'. It depends of the colors used in the document.
> If
> > you're using only cyan in your document, registration will be 100% cyan.
> If
> > your document contains only magenta and yellow, registration will be
> red. And


If your document contains only Magenta and Yellow, registration will *look*
red on the printed document but will actually appear on each plate at 100%
Magenta and 100% Yellow.

In a palette, I would suggest that instead of appearing in color that could
lead the user to think it might be a usable color for any other element on
the page (which it is strongly suggested not to do), it would be better to
put an icon there, of this mark. That way, users would know right away that
this "color" is special. Pros will feel at home and unaware users will not
want to pick a color that shows like a cross over a circle, unless they
learn what it is for.

Seems Cmyk is ignored this way.
>
>
> > if you have spot colors, registration won't be C=100% M=100% Y=100%
> K=100%. In
> > other words, registration can't be defined out of the document's
> context.


Right. The spot color will be part of the Registration color. In a 5-color
job, CMYK+1 spot, registration will be made of those 5 colors, at 100% each.
So will appear on all 5 plates.

I hope my explanation is clear. Please feel free to get back to me for
further details or precisions if needed.

Louis

> Registration should just be added in the software's color list for any
> press
> > work.
>
> ??
>
> > Color swatch draft
> > <
> http://create.freedesktop.org/wiki/index.php/Swatches_-_colour_file_format/Draft
> >
> >
> > The name and space attributes shouldn't be mandatory. A color doesn't
> need a
> > name to come into a palette and many palettes are just a arbitrary
> > "geometrical" division of the possibilities of color model. When you
> have
>
>
> Just numerical kind of colours are not precise.
>
>
> > #003399 in a palette, it's not because it looks like anything in real
> life,
> > it's just because its neighbors are #003366 and #0033CC. It just shows
> > different possibilities of RGB, whether you're using sRGB or AdobeRGB
> doesn't
>
>
> It would be nice in having a reference to colour spaces.
>
>
> > matter. The same applies to "Black 20%" (or C=10% M=20% Y=30% K%). There
> are a
> > lot of such palettes where neither the name or the color space have any
> > importance. By the way, Lab and XYZ don't need any color space since
> these are
> > device-independant models.
>
>
> Lab and XYZ need a colorimetric reference, in ICC context to white, in a
> more general context viewing conditions and physical intensities.
>
> kind regards
> Kai-Uwe Behrmann
>
> --
> developing for colour management
> www.behrmann.name + www.oyranos.org
>
>
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> CREATE at lists.freedesktop.org
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>
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