[pdftex] Colour profiles and pdftex

[George N. White III]

On Sat, Sep 5, 2009 at 6:09 AM, André Bellaïche<abellaic at math.jussieu.fr> wrote:
> Hello,
>
> I have gone into many troubles with a printing house recently about colour
> profiles or workspaces of included illustrations. The printer complained
> very much about colour profiles for image files embedded in the pdf file,
> although the book was in black, and all the illustrations had been converted
> to black and white or gray level.

Grays can be very difficult to get right.  If you have images such as
photographs where certain details need to be visible in (photocopies
of) print versions, then you need either a very cooperative printer
(almost impossible to find) or you have to take full advantage of
the prepress tools for color management.

> These profiles or workspaces have names as Fogra 27 or Dot Gain 15%.
>
> I know nothing about the subject, and could hardly find something about it
> on the Web, or in the books about Illustrator and Photoshop you can find in
> bookshops. So, these are my questions.
>
> 1) Where can I find both general and precise information about the subject
> (books or url's)?

Standards such as PDF/X are designed to make prepress more
reliable in automated workflows.

americanprinter.com: tends to be wieghted towards product advertising, but
contains useful information and is read by print shop staff.

<http://americanprinter.com/prepress/color/printing_implementing_color_management/>

wikipedia.com: PDF/X, "ICC profile"
Google: site:adobe.com PDF/X "ICC profile"

Book: "Exploring Digital PrePress: The Art and Technology of Preparing
Electronic Files for Printing" by
Reid Anderson

> 2) Is there a default profile included by pdftex in the files it produces?
> What does pdftex do with the profile of included images, which can be of
> various sources: Adobe Illustrator, Photoshop, Mathematica, Geoplan... ?

No.  In N. America many shops assume SRGB if no profile is provided.
Many LCD displays have an SRGB setting that is adequate for simple
tasks, but for careful work factors such as age and ambient light will
affect colors.  You will have to save the illustrations using a tool that
supports the appropriate PDF/X standard.

See <http://www.tug.org/pipermail/pdftex/2003-October/004490.html>
for an example.  You can use Adobe Apps to create PDF/X.  Unless your
use of color is very simple, you should invest in a colorimeter such as
Pantone Huey, which will help to ensure that the printshop sees the same
colors you do.

> 3) Is there a way to change the default output profile of pdftex to get more
> bold printing when one uses the Knuth Computer Modern fonts, which prints
> much to pale in most cases?

No.  The fonts were designed that way, but some print shops have problems
with the thin lines (dropouts).   There are other fonts that may be more suited
to a particular document, but the choice is limited if you need maths.  There
are some documents on CTAN that compare the options for maths using
Type 1 fonts.

> André Bellaďche

These days, print shops expect authors to do much more of the work.  It is
difficult to achieve top quality using only free tools.   Most shops are used to
working with documents created using Adobe tools, so it is generally a
good idea to save all the illustrations with the appropriate Adobe tool.

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia