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I'm working for a company making glass walls with prints on it. It works fine with images but when I send them something with vector it becomes pixelated after printing, they also reported that on big white surfaces there were some small black shapes and when i checked the file there were nothing there, also no anchor points etc.

I use illustrator and save my files in 150 DPI CMYK High Quality Print sizing the image 1:1 to the actual size, I think it's something to do with the printers program generating anomalies because I need to save vector images somehow else.

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    What is the file type you sent? As in the extension? The 'DPI' you talk about suggests .jpg or .png and those are definitely not vector files.
    – Vincent
    Commented Jan 23, 2023 at 11:34
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    which vector format are you sending?
    – JoSSte
    Commented Jan 23, 2023 at 19:19
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    Unless the printing is being done by a plotter, the file is getting rasterized at some point during the workflow. Identify that point, and you'll have your answer.
    – Mark
    Commented Jan 24, 2023 at 0:00
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    illustrator has no DPI setting.
    – joojaa
    Commented Jan 24, 2023 at 4:59
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    @ricsi It’s not so much that DPI doesn’t matter. The settings you mention do not exist for Illustrator files, they only pop up when exporting to raster formats. Which files do you actually send to the printer? AI files? PDFs? JPEGs/PNGs/TIFFs? Commented Jan 24, 2023 at 13:16

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If a file format specifies DPI, it is most probably not a vector file. DPI, dots per inch, indicates the amount of pixels over the width of an inch in the resulting file. This is inherently a pixel thing.

You may want to talk to the printing company to correctly submit vector files and ask them what file format they prefer for vectors. They will most probably want an .eps or a .pdf.

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    I am a bit stubborn. DPI = Dots per inch. PPI = Pixels per inch. I know you know. :)
    – Rafael
    Commented Jan 23, 2023 at 18:13
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    @Rafael I know you know I know. Note the phrasing 'indicates' rather than "is equal to' 😉
    – Vincent
    Commented Jan 24, 2023 at 0:01
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    Using a PDF doesn't mean anything in this situation. A PDF can contain both vector and bitmap graphics. You have to check both your PDF and the printer's procedures to identify the problem. You have to make sure your vector artwork isn't converted to bitmaps in the first place and then that the printer handles them correctly.
    – Gábor
    Commented Jan 24, 2023 at 13:36
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    @Rafael when the term DPI was invented, pixels and dots were the same so there was no need to make a distinction. It's not at all unusual to see it still used in its original meaning, depending on the context. Commented Jan 24, 2023 at 17:08
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    On the press, I expect the quoted 150 was probably lines-per-inch ( or LPI ), and that was actually expensive and therefore rare. 135lpi would have been high-end magazines; newsprint would have been maybe 100-110, but as low as 80=ish
    – Yorik
    Commented Jan 25, 2023 at 15:15
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I've previously run into a similar problem when trying to print high-resolution artwork for circuit-board manufacturing: the prints were on transparencies to allow for UV-photo-resist exposure and so had to be accurate, with no stray pixels. All artwork was done in a vector software.

The conclusion was that it depended on a number of factors. Updating the printer drivers (especially using the ones downloaded from the printer manufacturer, rather than the the plug-and-play ones) was a big part of it, though I expect given the sort of printer you’re using, this would have already been done.

Otherwise it seemed to be software dependent: printing within the vector program (directly from Adobe, Inkscape, Gimp, etc.) did cause artefacts to different degrees. Exporting to PDF and printing from there was better but often had other issues (the vector output in the PDF would appear as horizontal ‘blocks’ or ‘bands’ about 5 mm wide, which would separate when printing). Doing the artwork directly as a PDF, using LaTeX + TiKZ gave good results. We used multiple laser and inkjet printers and found varying results. Even a $10k Epson designed for high-resolution art printing had issues: we often found random stray dots (particularly on the laser printers) which seemed to be simply stray toner (this was at a single physical print dot size; important to us at that scale, but perhaps not important on the macro scale).

Ultimately we never found a complete solution: the issue seemed to be a mix of the way the software generated the data sent to the printer, and the way the printer converted that data into the physical print operation.

Beyond checking the drivers, the best you can do is probably to try different formats: ask the people who own/run the printer specifically what format they prefer. Try sending them a 300 DPI PDF for starters and see if it makes the problem go away or changes something elsewhere.

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It sounds like something weird is happening when the company is converting the file for print. This could be due to the file type or color profiles. During my time in print production, I was taught that 300 PPI is a good practice for saving raster files.

I would reach out to the company and find out their preferred file types, color profile (if this is an online company they might prefer RGB file submissions), and resolution, then go from there :)

Good luck!

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  • A color profile has nothing to do with resolution. It is related to... color.
    – Rafael
    Commented May 19, 2023 at 15:01

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