Question about printing process

Discussion in '4-Color Offset Presses +' started by generalbatzorig, Aug 31, 2017.

  1. generalbatzorig

    generalbatzorig Member

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    I design books and catalogs. I have a question about preparing images for press.
    If I prepare my file for a book on Indesign and submit it to the printer, does it go through any pixel based program (such as PDF or Photoshop) at the print shop? Or do they convert the pages directly to printing negatives. I am asking this because if they convert my Indesign file to pixel images, there might be a chance that the quality of image files may change.
    I want to find out every step involved in printing process. So that I know what affects the final image quality.
    I found out recently that exporting to PDF from InDesign can degrade the image sharpness, and it has became of concern to me.
     
  2. generalbatzorig

    generalbatzorig Member

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    No one wants to answer my question? Or may be I didn't put my question clearly.
     
  3. xfactor printing

    xfactor printing Senior Member

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    PDF files contain raster and vector objects. When the plates are made everything will be converted to cmyk dots. Images in a PDF can be resampled if the file is "excessively bloated" and the prepress dept thinks it will clog the workflow, but it shouldn't have to be. Communication is key.

    Ask the press for the optimal PDF settings for their workflow. Get a test print and discuss it with their prepress department. For fine linework within a color/grayscale image there can sometimes be a small gain using a higher pdf resolution that their default... discuss it with the prepress dept. Work back from the final print lpi / screen.
     
  4. generalbatzorig

    generalbatzorig Member

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    Thank you xfactor for answering my question. It was helpful in my learning process. I would like to learn about the term "excessive bloating". Does it refer to PDF file from an image that had high pixel density?
    I am sure my previous entry wording was not so clear. As a result you mostly wrote about working with PDF files.
    1) But what if I provide the printer with an Indesign file with all the links and images included properly?
    2) Does the printer convert the pages directly to CMYK dots, or do they convert it to a pixel format first and then to CMYK dots?

    As I have tested on my own. InDesign has its own pixel dimension. And if the image frame and image resolution are not aligned perfectly with InDesign pixel dimension, it rearranges pixels to InDesign resolution when exporting to PDF. As a result the image file looses its original pixel clarity. Even if you prepare the link photo to 300 dpi and export it to 300 dpi, the misaligned image frame will cause all pixels of the link to be rearranged. That means one pixel could be changed to 2-4 pixels, and the original image quality and sharpness changes. It is hard to explain, but I hope you understand that.
     
  5. xfactor printing

    xfactor printing Senior Member

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    Sorry, I supply everything as PDFs so that's what I'm familiar with.

    What I mean by 'excessive bloating' is this: I've had some booklets printed by an outfit that had great presses while their prepress was archaic. The prepress department was not impressed when I supplied 600 dpi PDFs because it choked their workflow on their old really slow RIP.

    That's why I'd recommend communicating first. If you supply color images at something huge, like 1200 DPI, meaning the booklet will be gigabytes larger, there's a higher probability the prepress department will resample down before feeding it to their platemaker. My experience is that expensive things like platemakers / RIPs are often older and slower than computers. Best to communicate beforehand with the prepress dept and see what their settings are. Will they run your native resolution document directly to their platemaker? Do they have their setup set to resample down if over x-dpi before outputting to the platemaker?
     
  6. xfactor printing

    xfactor printing Senior Member

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    It's a good discussion. I know what you mean by the sharpness/pixel quality lost every time you resample. It's a fact of life for me given the computer power I have available. I have the photo resolution coming in which is usually higher now. Then I resample once to my working resolution where I apply cropping and sharpening. And then there is the printer resolution. Depending on what I'm printing, I still use 300 dpi for standard items such as rack cards. I use 600 dpi working resolution for higher quality jobs which gives me some room. I also print some things on both digital and offset and 600 dpi gives me enough to get great results.
     
  7. Abhi

    Abhi Member

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    The vector files do get conveted to raster format but that raster resolution is high and no quality loss occurs.
     
  8. xfactor printing

    xfactor printing Senior Member

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    Vectors should stay vector in the PDF and any imposition, etc. until being rasterized to C M Y and K plates.
    There could be exceptions where complicated effects get rasterized due to software limitations - I've had to rasterize and flatten some text effects with clipping, transparency, shadows, and raster images to make sure a glitch didn't surprise me in the final output...

    Now raster images in the origin file... I try to stay working at the same or a multiple of the output resolution. I think it's better to work at 300 dpi or 600 dpi if the output resolution is going to be 300 dpi. I think working at 325 dpi would create more softening as a hypothetical example. Would be glad to hear others thoughts on this.
     

  9. RUJHSB

    RUJHSB New Member

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    Hi ABHI.
    see attached Sample for exporting to PDF Press Ready files.
    thanks
     

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