[Scribus] Setting linescreen when printing pdf file
Wed Jul 21 04:44:18 CEST 2004
? (At) 12h49 +0800 19/07/04, Craig Ringer ?crivait (wrote) :
>On Mon, 2004-07-19 at 05:57, Wayne Maeda wrote:
> > Is it possible to print out a pdf document (with text and
>graphics) in Windows
>> so that the graphics print out at 75 lpi while the text remains crisp and
> > dark black? I was under the assumption that it could be done. Most of the
>> newspapers that I deal with request their ads to be in pdf format. They must
> > be printing them out at a certain linescreen somehow someway.
>At my workplace (a newspaper) we prefer PDFs from clients. Our printer's
>RIP is what makes the decisions on linescreen, etc, and it clearly
>treats text and graphics differently. It's obvious when we've had to use
>a TIFF instead, or when a client has supplied a PDF of an image of the
>ad, because the text comes out with awful grainy edges due to the
This is an interesting discussion. I apologize in advance for all the
shortcuts in the following answer; we could write a book on that
It is important to distinguish between "resolution" (dpi) and
Please also note that it should be clear at begining that the word
"resolution" itself covers many grounds. INPUT resolution differs
from OUTPUT resolution and this can lead to confusion. You have
resolution of the image file, resolution of ripping and resolution of
output. Please read on.
RIPping implies 2 operations.
The first one being to transpose the editable code of the DTP program
into an uneditable one, at a certain resolution in dpi. This usually
varies from 300 dpi to 2400 dpi depending upon the software and
material used and of course on the result needed.
Some RIPs apply the same resolution to all elements on the page. It's
easy to understand: all elements will be ripped at the same
Other RIP will do what is called "dual resolution ripping". In that
case, the rip will distinguish between vectors and will rip them at a
high resolution such as 2400 dpi, and bitmap images will be ripped at
300 dpi. The benefits for the workflow are lighter traffic on the
network and faster process. A file ripped at one single high
resolution is lots heavier than its counterpart at dual resolution.
The reason why we can treat images at this low 300 dpi resolution is
that images usually come at 300 dpi. So 300 dpi in, 300 dpi out. As
for vectors, (type, vector graphics, logos, etc.), in order to
achieve a crisp job, we need a high resolution ripping at, say, 2400
dpi (it could be 1200 and still be OK). In anyway, the RIPping
resolution is determinent on the end result. Keep in mind there is
nothing absolute and it is not necessary to have dual resolution
ripping to achieve professionnal results, nor it is better to rip at
one single resolution. It is a matter of workflow and each has its
benefits and drawbacks.
The second operation consist of applying a linescreen because the
process of printing needs it to reproduce all the variations of a
gray scale from 0% to 100%. Applied to color and with a mix of only 4
colors, a press can reproduce what is usually being accepted as
Linescreen is the trompe-l'oeil by excellence printing has lived on
for decades. It makes the human eyes believe what they see is grey
when it's black, and what they think is thousands of colors is only
"4-color process" Cyan, Magenta, Yellow and Black. As per nowaday's
standards, we can affirm there would be no printing without
linescreen, with all the reservations this assumption implies.
Linescreen may vary from 15 line per inch (lpi) to 200 lpi and even
much higher on high-end systems. You can apply a low or a high
linescreen to a high resolution file, and vice-versa. Various
combinations, various results. For a newspaper, printed on a
high-speed web press on cheap, uncoated, newsprint paper, the need
for a low linescreen is obvious. You don't want ink to "plug" your
images, so you need big dots spaced by lots of space because this
paper will allow ink to penetrate deeply into its fibers and
"spreading". This of course has an effect on the final result. To
avoid this, we use low linescreens. On the other hand, we need high
linescreen to achieve a very well defined image such as in magazines
and books of art. High resolution and high linescreen provide the
best combination to reproduce an image at its best. (Not to forget
good pressmen! - but I told you before there would be shortcuts!)
On top of that, the imagesetter or platesetter will also have a role
to play in the end: the "output resolution", the grid by which the
laser will actually expose the photosensitive material, can be
generally set to resolutions such as 1200, 2400 or 3600 dpi. This
output resolution determines the quality of the linescreen DOT (how
precisely that dot is defined). Again, the smaller the grid, the
"cleaner" the dot. The cleaner the dot, the clearer the image.
So yes, absolutely, the linescreen is applied to the entire page. To
what extent does it affect the elements? First, there are no "dots"
to see in a 100% of any of the CMYK color since the whole area is
filled with that color. But don't get me wrong, since all "colors"
will be transposed in the CMYK model, it is very important to
consider that combination to determine if it is suitable for a tiny
detail such as body text. For instance, if you have a green at 100%
that will be printed using CMYK, you better be cautious on that green
"recipe"... 80% Cyan + 80 % Yellow produce a nice Green that you may
want to use at 100%. But the plates will contain 80% of C + 80% of Y
and the linescreen will show its dots. If the linescreen is low, such
as 75 or 85 lines per inch, any human eye will be able to distinguish
the dots. At a 150 lines (the standard for magazines), it takes a 10X
Linescreen is a necessity, it is not evil. ALL printed material is
screened. A 150-lines job can be of very high quality. Even newspaper
don't look so bad.
Ugly jaggy edge I suspect is caused by an earlier manipulation in the
process that will only be cruelly revealed by the linescreen,
especially if it is a low one.
A TIFF image has a fixed resolution. It can be anything. Usually, 72,
150, 300, 600 dpi. This depends on the scanner settings or the
settings at which the image was saved. If the TIFF's resolution is
too low, there is no way this image will produce good result on a
press. Also, if the black generation came from the RGB world, as I
wrote in an earlier message, that black may not be black only and
could end up beeing 5% or 7% short of a full 100% black. Then, of
course, it will be screened and of course if it is too small an
element, low (and even high) linescreen will reveal the weekness of
the whole process if that element is not "solid" ink (100%).
A PDF is a vector file and has no predefined resolution until it is
actually ripped (fixed). Only, the pictures in the PDF can be
converted, at PDF creation, to a specific resolution (this is why the
graphic art industry has come up with specifications such as
PDF/X-1a, to avoid unusable PDFs). A vector element can be scaled to
any value and will only reveal its limit at very large scale where
the curves will show their defects if they were poorly drawn. In
theory, if the curve is well defined, there is no limit to scaling.
Once ripped, the vector is not vector anymore and if you enlarge it
enough, you will see the jaggy edge of the curve line at ripping
resolution, with the help of a good magnifier.
A poor resolution in the early stages can only be reproduced as it
is, no matter how high we RIP and at what high value linescreen it is
output, at which output resolution . The linescreen dot may be as
sharp as you can imagine, if the image is pixellized... it will be
"nicely" and "perfectly" reproduced on the film/plate, for you to
determine in how many copies on the press.
Thank you for reading!
>Essentially, I'm pretty sure it's the RIP's job in a PDF workflow.
>> Unfortunately, the printer that I'm dealing with currently, does
>>not take pdf
>> files. They want it camera ready.
>Heh. There aren't even any (newspaper) printers in my STATE (Western
>Australia) that accept camera ready jobs anymore. We were forced to go
>all digital, kicking and screaming, because of this - and frankly I
>would've liked to stay with our hybrid process until we could've moved
>to InDesign. Now we're stuck with Quark 4 on MacOS 9 for the forseeable
>future. (It should be pretty obvious why I'm interested in Scribus).
>> Which means I have to take it to another
> > place to have it printed out at the specified linescreen. Except that this
>> other place does not have the software that sets the linescreen. End result:
>> I have this pdf document with no way to print it out properly. Hmm.
>GhostScript appears to have some screen controls. '-dCOLORSCREEN=' and
>'-dDITHERDPI' may have some potential. I'm unable to test if they do
>what you need right now, I'm sorry, but you might want to look into
>them. They're documented briefly in 'Use.html' in the gs docs.
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