Mats Broberg said this at Sun, 25 Jul 2004 12:01:03 +0200:

- I don't quite understand how ConTeXt:ers deal with solid PMS spot colours

Mats, have a look at: http://pragma-ade.com/general/manuals/msplit.pdf Disclaimer: I haven't used spot colours yet, but I know it's in a manual. :) -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Adam T. Lindsay atl@comp.lancs.ac.uk Computing Dept, Lancaster University +44(0)1524/594.537 Lancaster, LA1 4YR, UK Fax:+44(0)1524/593.608 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Thanks for all the responses. I got some very useful information here. I do have a couple of quick follow-up questions. On Sat, Jul 24, 2004 at 03:21:39PM -0500, Bill McClain wrote:

Different shops might have different requirements, but Bookmobile simply requires an exact image of the book, page size defined to be the paper size. Easy.

You're referring to just the interior, right? I would think that covers have to have a bit of bleed, no?

This has all been for digital printing and perfect-bound paperbacks.

Pretty much what I'm doing for now. As a matter of fact, partly inspired by your example, I'm attempting something rather similar to your publishing biz--though not in direct competition, I hope and believe. On Sun, Jul 25, 2004 at 12:01:03PM +0200, Mats Broberg wrote:

Being a newbie when it comes to ConTeXt, but having worked in the commercial printing busines for a decade, I would say that the majority of printers actually prefer PDF files rather than Quark, InDesign or Pagemaker files. At least that is the case in Europe, and it would suprise me if it is not the same situation in USA.

Well, yes. Many printers here do prefer PDF. However, there's a small problem in some cases--I know this is true for Kinko's, and was wondering if it's true for regular printers, too: they think that PDF means "Adobe PDF"--i.e. they believe that Adobe software is *the* way to produce PDF, and are mostly unaware that there is such a thing as a PDF standard. Now, I don't fully understand the issue, but apparently Adobe software doesn't entirely follow the published specs, whereas TeX does. And some processing software seems to be designed specifically to work with the quirks of Acrobat output, and sometimes has trouble with PDFTeX output.

- Also, I don't know whether it is possible to downsample images in PDF's that you generate from ConTeXt. If it is, avoid it.

That raises an important question: if downsampling is done, is it obvious what ConTeXt commands cause it to happen?

The printer expects CMYK images (not RGB!) where the resolution is approx. 2 times the screen count in the final print, @ the physical size on the paper. So if you have an image in your PDF that is 10 cms /4 in. wide, and you want it printed in a 150 lpi (lines per inch) screen, make sure the original resolution is 300 dpi @ 10 cms / 4 in.

Now that's interesting. I imagined you would get the best results with images that were designed exactly at the printer resolution. -- Matt Gushee When a nation follows the Way, Englewood, Colorado, USA Horses bear manure through mgushee@havenrock.com its fields; http://www.havenrock.com/ When a nation ignores the Way, Horses bear soldiers through its streets. --Lao Tzu (Peter Merel, trans.)

On Mon, Jul 26, 2004 at 11:33:03PM -0700, Brooks Moses wrote:

At 11:15 PM 7/26/2004, you wrote:

...

On Sat, Jul 24, 2004 at 03:21:39PM -0500, Bill McClain wrote:

...

...

The printer expects CMYK images (not RGB!) where the resolution is approx. 2 times the screen count in the final print, @ the physical size on the paper. So if you have an image in your PDF that is 10 cms /4 in. wide, and you want it printed in a 150 lpi (lines per inch) screen, make sure the original resolution is 300 dpi @ 10 cms / 4 in.

Now that's interesting. I imagined you would get the best results with images that were designed exactly at the printer resolution.

You might, but that would only be true if you also have the image aligned exactly with the printer resolution -- which is unlikely to be the case unless you do it explicitly. Having the 2x-or-higher resolution means that the downsampling in the printing process will produce an acceptable result no matter what the alignment is.

Beyond that, I suspect there are also some effects involved in the fact that the printer is creating a screen rather than dots of pure color; there are things going on in the screen that are on a finer scale than the line spacing, and having the higher-resolution to base them on probably produces a better result.

- Brooks

For a screened picture, you can often get away with less than twice the lpi, especially if there are no sharp transitions. On the other hand, pure black-and-white line drawings are best printed without screening. For such images, higher resolutions are better. 600dpi is enough for losing jaggies. Up to a point, more is better, but printer resolution (2400dpi or more) would produce very large bitmaps. -- Siep Kroonenberg

From: ntg-context-bounces@ntg.nl [mailto:ntg-context-bounces@ntg.nl] On Behalf Of George N. White III

As a general principle, it makes no sense for pdftex to provide image manipulation capabilities. Such capabilities are useful to a much wider audience than the users of pdftex, so there are lots of tools to do image resampling and format conversions. All that pdftex should do is support inclusion of pdf. The limited support for including png images is a convenience, but if you are being careful you would want to make pdf images.

-- George N. White III Head of St. Margarets Bay, Nova Scotia, Canada

Having checked the pdfTeX documentation, doesn't the internal parameter \pdfcompresslevel deal with this? The documentation says: "compress level This integer parameter specifies the level of text and in-line graphics compression. pdfTEX uses zip compression as provided by zlib. A value of 0 means no compression, 1 means fastest, 9 means best, 2..8 means something in between. Just set this value to 9, unless there is a good reason to do otherwise - 0 is great for testing macros that use \pdfliteral." Best regards, Mats Broberg

...

Having checked the pdfTeX documentation, doesn't the internal parameter \pdfcompresslevel deal with this? The documentation says:

"compress level This integer parameter specifies the level of text and in-line graphics compression. pdfTEX uses zip compression as provided by zlib. A value of 0 means no compression, 1 means fastest, 9 means best, 2..8 means something in between. Just set this value to 9, unless there is a good reason to do otherwise - 0 is great for testing macros that use \pdfliteral."

The compression this parameter controls is quite different. Without compression (e.g., \pdfcompresslevel=0) a PDF file consists of almost readable text. Even images can be stored in an ASCII encoding. Setting a non-zero value for \pdfcompresslevel applies a lossless compression algorithm to objects in the pdf file.

For exactness. Primitive \pdfcompresslevel influences lossless compression of 1) content of pdf objects 2) included PNG images (they are decoded and encoded again) In case of inclusion of PDF, it is put as it is (so compresslevel is not changed). JPG is also untouched. It was valid for pdfTeX version <1.0. I have no info about changes in this case. Vit Zyka

Am Di, den 27.07.2004 schrieb Matt Gushee um 08:15:

they think that PDF means "Adobe PDF"--i.e. they believe that Adobe software is *the* way to produce PDF, and are mostly unaware that there is such a thing as a PDF standard. Now, I don't fully understand the issue, but apparently Adobe software doesn't entirely follow the published specs, whereas TeX does. And some processing software seems to be designed specifically to work with the quirks of Acrobat output, and sometimes has trouble with PDFTeX output.

This is also true if you want to publish advertisements in journals - the journals/newspapers often require PDF prepared by Adobe Acrobat / Distiller. If you provide advertisements prepared by other means then it is your fault if something goes wrong. This is despite the PDF/X3 standard for preprint ready PDF documents. For this reason the claim of some commercial TeX-vendors to produce PDF which comes closer to the "quirks of Acrobat output" is not worth so much in practice. However, when you prepare documents for print regularly, then it is anyway best to have "your own" printer locally at hand - somebody you can trust and who wants to keep you as a customer. Then you can deal with problems arising and talk about solutions directly. So far I did not encounter problems with PDFs made by PDFTeX, but then I gave only documents to print in black and white or with colours where it does not matter if the red or blue is slightly brighter or darker. I dont know about printing-experiences of PDFTeX-prepared documents with colour separation, spot colours, trapping ... in conjunction with various media (glossy/matte paper ...) where it becomes more difficult. Yours sincerely Tobias Hilbricht

From: ntg-context-bounces@ntg.nl [mailto:ntg-context-bounces@ntg.nl] On Behalf Of Matt Gushee

Well, yes. Many printers here do prefer PDF. However, there's a small problem in some cases--I know this is true for Kinko's, and was wondering if it's true for regular printers, too: they think that PDF means "Adobe PDF"--i.e. they believe that Adobe software is *the* way to produce PDF, and are mostly unaware that there is such a thing as a PDF standard. Now, I don't fully understand the issue, but apparently Adobe software doesn't entirely follow the published specs, whereas TeX does. And some processing software seems to be designed specifically to work with the quirks of Acrobat output, and sometimes has trouble with PDFTeX output.

At one of the company I work for, we generate thousands of press-ready PDF manuals (250+ pp each) every year that are generated from XML source using XEP from RenderX - with no problems at all. So I don't think it is a requirement for printers that the PDF files are generated using Adobe tools.

Now that's interesting. I imagined you would get the best results with images that were designed exactly at the printer resolution.

True, for line art - but the "exactness" is unimportant. A common imagesetter resolution is 2540 lpi, so you may want to create your line art in that resolution. However, most printers prefer 1200 dpi (but not less) for line art, since images with a higher resolution become so large (memory-wise). Regarding halftones (color or grayscale), the commercial printing community rule-of-thumb is a resolution about 2 times the screen count. If your image is 10 cm wide on the scanner and you want it to be 10 cm wide on the paper, and you want the printer use a screen of 150 lpi, scan it at an optical resolution of 300 dpi. However, as I mentioned before, this holds true only if the physical image size and the final image size are the same. If the image is 5 cm wide on the scanner and you want it to be 10 cms wide on the paper, you need to scan it with a resolution of 600 dpi. Never increase the resolution of an already scanned image using software interpolation. Regarding using a higher resolution than 2-2.5 times the screen count, try to avoid it, since the photomechanical laws of process engraving doesn't give you a better final image anyway. However, pls note that I am talking about conventional lito offset here, and that I am talking about a conventional screen technology (amplitude-modulated screening). If you are using waterless lito offset, the screen count is usually quite a bit higher (300-500 lpi are not uncommon), which requires higher resolutions. Also, if you are using a different screening technology - e.g. frequency-modulated screening, or a hybride screening - your images may need to be of a higher resolution too. Talk to your printer. Best regards, Mats Broberg