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M
Milko con la elle
Known Participant
February 14, 2025
Answered

image resolution when saving as PDF

  • February 14, 2025
  • 1 reply
  • 577 views

good morning,

I need clarification regarding the resolution of images in a file saved as PDF/X-4:2010

I noticed that the resolution of an image present inside the illustrator document is heavily reduced when I choose downsampling, this happens despite the image resolution not reaching the downsampling value.

 

these are the setting:

FILENAMESOURCE IMG PIXEL SIZESOURCE IMG DIMENSIONSPDF SETTINGACROBAT INSPECTOR SIZEACROBAT INSPECTOR RESOLUTION
test risoluzione - 01.pdf24217 x 118116151,12 x 2999,99 @100ppiPDF/X-4:2010 - DOWNSAMPLING 300ppi if image res > 450ppi7266 x 3544 pixel (61511x30000 mm)118 pixel/mm
test risoluzione - 02.pdf24218 x 118116151,12 x 2999,99 @100ppiPDF/X-4:2010 - NO DOWNSAMPLING24217x11811 pixel (61511x30000 mm)393 pixel/mm

 

in both cases the starting image is the same

 

these are the questions:
- why does downsampling occur even though the image resolution is less than 300ppi?
- why is the image resolution changed even though the image is not modified in any way in illustrator after importing?

- why inspector show resolution pixel/mm instead of ppi ?

    Correct answer Doug A Roberts

    This sounds like a large canvas document problem.

    The first image is 100 PPI in a large canvas document, but that's with Illustrator's 10x scaling for large canvas. Maybe this gets lost in export, so a 100 PPI image becomes 1000 PPI, is downsampled to 300 PPI (really 30 PPI), and then is scaled back up in the PDF.

     

    I'll see if there's an existing report on this.

     

    Edit: this looks like the same issue:

    PDF files made on large artboards get downscaled incorrectly. – Adobe Illustrator

     

    @Ton Frederiks I see you commented there, does this look like the same thing?

    1 reply

    Doug A Roberts
    Community Expert
    Doug A RobertsCommunity Expert
    Community Expert
    February 14, 2025

    The first image is 3000 PPI (2.422 inches wide and 7266 px).

    The second is 10,000 PPI (the same in inches but 24217 px).

     

    Open Preferences > Units and change your page & ruler units to inches if you want PPI.

     

    What is the size of the Illustrator file?

    M
    Milko con la elleAuthor
    Known Participant
    February 14, 2025

    6640x2600 mm (200 mm bleed)

    Doug A Roberts
    Community Expert
    Doug A RobertsCommunity ExpertCorrect answer
    Community Expert
    February 14, 2025

    This sounds like a large canvas document problem.

    The first image is 100 PPI in a large canvas document, but that's with Illustrator's 10x scaling for large canvas. Maybe this gets lost in export, so a 100 PPI image becomes 1000 PPI, is downsampled to 300 PPI (really 30 PPI), and then is scaled back up in the PDF.

     

    I'll see if there's an existing report on this.

     

    Edit: this looks like the same issue:

    PDF files made on large artboards get downscaled incorrectly. – Adobe Illustrator

     

    @Ton Frederiks I see you commented there, does this look like the same thing?

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