Re: PDF, spot colors,RIPs, and ink jet printers
Re: PDF, spot colors,RIPs, and ink jet printers
- Subject: Re: PDF, spot colors,RIPs, and ink jet printers
- From: Matt Louis <email@hidden>
- Date: Fri, 24 Aug 2012 15:17:59 -0500
- Acceptlanguage: en-US
- Thread-topic: PDF, spot colors,RIPs, and ink jet printers
Hi Steve,
If this is true then I ask to what extent it matters. Transparencies are
rendered to pixels at one stage or another in all print workflows and
there is no right or wrong appearance for spot color gradients except for
closed-loop systems with arbitrary reference. As for the solids, even
Pantone changes the CIElab values on occasion. I have encountered problems
with all four formats. Using Photoshop as a RIP may render differently
than a dedicated RIP sometimes but its equal opportunity for better or
worse. We RIP 1000+ pages per day for offset printing and rendering errors
are very rare (none, one or two a month that we are aware of). PDFs can
process dynamically due to output intents, page boxes, xmp data and so
forth which can make the requirements for a workflow or RIP configuration
less clear. I find with problems files that the designer isn't even able
to rasterize a page to their own liking; I call these bad files because
they must be reworked to render correctly regardless of downstream
workflow.
My gripe with PDFs happens when viewing, or Ripping to screen.
1. Line widths that should be displayed less than 1 monitor pixel width
are displayed no less than the size of a monitor pixel for obvious
reasons. Acrobat has to decide to show or not show the object.
Unfortunately 0.00 mm width lines are displayed too.
2. Page display preferences can (a) make outlined fonts look
unrealistically chunky and (b) show white lines that will not exist in
print.
3. The default rendering intent for cmyk to monitor RGB is relative
colorimetric and it is not intuitive for clients to "simulate paper" to
see dynamic range realistically.
4. Multi-page mixed stock/surface PDFs can only have one output intent
rather than let this happen on a page level basis.
5. Overprint preview is not forced in non pdf/x files and even then can be
over-ridden in preferences.
These types of things will entitle customers to say something was or was
not in the proof that was not matched in print. Toggling Page Display
preferences is necessary to see some documents correctly. No single
setting works for all PDFs. Considering this I still would not suggest
against ripping PDFs to screen. Dedicated pixel formats can be misleading
too.
Matt Louis
On 8/24/12 8:27 AM, "Steve Miller" <email@hidden> wrote:
>I've been doing some research with PDF files and RIPs. We want to have a
>PDF only workflow and one RIP vender is saying we should not use PDF
>files. Instead, they recommend .eps, .tif or .jpg.
>Here's a reply from one RIP vender.
>
>"The pdf print engine is implemented as a base feature in the" (enter any
>vender name here) " RIP programs. It has advanced handling of pdf and pdfx
>file formats. It was necessary for" (enter any vender name here) "to add
>this feature due to Adobe's constant alteration of the pdf encoding
>process and handling of transparencies, spot color handling in gradients,
>and compression methods. There is a basic flaw in the conversion of spot
>color in the pdf format to the rastered ink dots of an inkjet printer.
>This is a problem that all RIPs have.. It is a problem inherent in the pdf
>format being rendered into the inkjet dot format. The repeat printability
>of colors suffers in this format. While Adobe also alters the EPS format,
>color consistency from print to print is stable."
>
>Is this a true statement?
>
>--
>Steve Miller
>Color Management Specialist
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