PDF Export Resolution Problem

[Huwge]

Has this thread been resolved? I am having the same problem in 2021 running Affinity Designer v1.10.4 on OS11.6.1. The PDF created is, I am sure, 300 dpi A5 size ( with bleed and printer marks), open it in other PDF capable apps on Mac or PC and it appears fine, but according to the info in the Finder it has a resolution of 481 x 692.

This causes problems when uploading artwork to online printers whose prechecks insist that the PDF isn't of high enough resolution to print well.

Just in case anyone else is looking for the answer...
On further investigation this appears to be a MacOS finder feature (problem). The 'resolution' information for PDFs, by default, is shown in Points. The only alternatives appear to be using inches or millimetres. I think this will be because a PDF file is not really a raster image with a fixed resolution and as such the 'resolution' can be different depending on how you view the file or your output method or device, so they give the dimensions instead.

Edited November 10, 2021 by Huwge
additional info and possible explanation

[Hangman]

@Huwge, the info in the Finder is correct, as mentioned previously in the thread, the Finder is displaying the size of the PDF using points (not pixels).

A5 - 148mm x 210mm = 419.76pt x 595.44pt

Exporting from Affinity Designer with bleed, crop marks, colour bars and page information will result in larger page dimensions to accomodate the printers marks so you end up with a file that is 480.77pt x 691.95pt.

PDF's use the same basic measurement unit as PostScript, i.e., 72 points = 1 inch which is the device independent way of stating dimensions.

Using pixels is a device dependent way of stating dimensions, i.e., the absolute size of a graphic object on a display or printed page depends on the resolution of the display or printer so while you can specify sizes in pixels while creating a PDF you have to remember that pixel sizes differ. A 300 x 300 pixel image will be 1" x 1" square on a 300dpi printer, but 3" by 3" on a 100dpi monitor.

[lacerto]

4 hours ago, Huwge said:

On further investigation this appears to be a MacOS finder feature (problem). The 'resolution' information for PDFs, by default, is shown in Points. The only alternatives appear to be using inches or millimetres. I think this will be because a PDF file is not really a raster image with a fixed resolution and as such the 'resolution' can be different depending on how you view the file or your output method or device, so they give the dimensions instead

Yes, I agree. It is a bit silly to report physical dimensions as "resolution". For raster images, the Info panel shows the pixels and uses the label "Dimensions". I think it should logically be the other way around, and at least it would be useful to display the units. In addition either there seem to be internal limitations (possibly based on PDF/PS specs) or assumptions on the used units as the PDF attached below, containing a 1000x1000px image with 1px per cm nominal resolution should logically display 28,346.5pt x 28,346.5pt as its "resolution" in the Info panel (in centimeters, that is 1,000 x 1,000 cm), as it does when using Adobe apps (Acrobat or Photoshop), but it shows 14,400 x 14,400 (pt) in the macOS Info panel, instead. Affinity apps seem to make the same mistake when they open this file and determine its physical dimensions.

Either way, the Info panel of macOS cannot be used to check whether the (possible) raster content within the PDF meets the PPI specs determined by the print shop. The file below, if its nominal resolution were changed to 4,800ppi (as could be if set by a scanner) -- certainly something that meets print shop minimum PPI resolution requirement for raster images -- would show (correctly) 15 x 15pt as its resolution in the macOS Info panel.

foolish.pdf

 

[Hangman]

• PDF Versions 1.3 (Acrobat 4.0) and earlier the maximum PDF page size was 45" x 45"
• PDF Version 1.4 (Acrobat 5.0) and 1.5 (Acrobat 6.0) the maximum PDF page size was 200" x 200".
• PDF Version 1.6 (Acrobat 7.0) and newer the theoretical PDF page size is 15,000,000" x 15,000,000" but most programs do not properly support any sizes above 200" x 200".

FWIW, opening the file in Foxit PDF Reader displays the full file dimensions...