12 Replies Latest reply: Mar 10, 2011 10:11 AM by efg5 RSS

    Determining dpi using Adobe 9 Standard

    efg5 Community Member

      Using Adobe 9 Standard, how can I find out the dpi of a pdf someone sent me?

       

      Thanks!

        • 1. Re: Determining dpi using Adobe 9 Standard
          Dave Merchant CommunityMVP

          PDF files do not have "a DPI" - every pixel-based page element can be different, and the text and some graphics are vector-based (so have no pixels to count).

          • 2. Re: Determining dpi using Adobe 9 Standard
            Bill@VT CommunityMVP

            You may be able to get some of the information on individual items by using preflight to check the document.

            • 3. Re: Determining dpi using Adobe 9 Standard
              efg5 Community Member

              Huh?

               

              So you're saying that although I tell my scanner to scan at 600 dpi or 300 dpi, the resulting PDF has no characteristic resembling dpi?

               

              Then how does one describe the the resolution of a PDF?

              • 4. Re: Determining dpi using Adobe 9 Standard
                efg5 Community Member

                Adobe 9 Standard doesn't have the "preflight" feature.  (I believe only Adobe 9 Pro has it.)

                • 5. Re: Determining dpi using Adobe 9 Standard
                  Bernd Alheit CommunityMVP
                  So you're saying that although I tell my scanner to scan at 600 dpi or 300 dpi, the resulting PDF has no characteristic resembling dpi?

                  You can check resolution of images in PDF documents with the preflight tool of Acrobat Pro.

                  • 6. Re: Determining dpi using Adobe 9 Standard
                    Bill@VT CommunityMVP

                    Images are stored in a block in a PDF and have their own resolution. There is no native resolution to the PDF itself, but is set in the parts. You should be able to determine the resolution of scans and such by using Extract All Images. Those extracted images should be identical to what is stored in the PDF to my understanding. You can then check them in a graphics editor or tool like IrfanView.

                    • 7. Re: Determining dpi using Adobe 9 Standard
                      efg5 Community Member

                      Bernd Alheit wrote:

                       

                      You can check resolution of images in PDF documents with the preflight tool of Acrobat Pro.

                       

                      Adobe 9 Standard doesn't have the preflight tool.

                      • 8. Re: Determining dpi using Adobe 9 Standard
                        efg5 Community Member

                        Images are stored in a block in a PDF and have their own resolution. There is no native resolution to the PDF itself, but is set in the parts. You should be able to determine the resolution of scans and such by using Extract All Images. Those extracted images should be identical to what is stored in the PDF to my understanding. You can then check them in a graphics editor or tool like IrfanView.

                        There aren't images in the documents I'm working with, only text.

                         

                        When I can tell my scanner 600 or 300 dpi, how is it the resulting PDF has no native resolution?

                        • 9. Re: Determining dpi using Adobe 9 Standard
                          Bill@VT CommunityMVP

                          If you got the PDF from a scanner, then you should have pages of images (one image per page). If you do not, then you probably ran OCR on the result. If you used ClearScan, then the images are replaced by fonts and you can check the font properites. Otherwise, you should have a collection of images that can be exported.

                          • 10. Re: Determining dpi using Adobe 9 Standard
                            efg5 Community Member

                            Bill@VT wrote:

                             

                            Images are stored in a block in a PDF and have their own resolution. There is no native resolution to the PDF itself, but is set in the parts. You should be able to determine the resolution of scans and such by using Extract All Images. Those extracted images should be identical to what is stored in the PDF to my understanding. You can then check them in a graphics editor or tool like IrfanView.

                             

                            If I have to use a graphics editor like IrfanView, then it sounds like I can't find out the dpi of a PDF using Adobe 9 Standard. Right?

                            • 11. Re: Determining dpi using Adobe 9 Standard
                              Dave Merchant CommunityMVP

                              We've told you - there is *no such thing* as "the DPI of a PDF". Each page element has an independent value (or none at all) and they can be, and often are, widely-different between elements on the same page.

                               

                              Even if your file is a scan without OCR, so it contains a single image of each scan, one per page - the PAGE has no resolution. The image ON the page does, but that's an entirely different concept. Acrobat Standard does not allow you to inspect page elements to see their individual properties; that's a feature of Acrobat Pro.

                              • 12. Re: Determining dpi using Adobe 9 Standard
                                efg5 Community Member

                                Dave Merchant wrote:

                                 

                                We've told you - there is *no such thing* as "the DPI of a PDF". Each page element has an independent value (or none at all) and they can be, and often are, widely-different between elements on the same page.

                                 

                                Even if your file is a scan without OCR, so it contains a single image of each scan, one per page - the PAGE has no resolution. The image ON the page does, but that's an entirely different concept. Acrobat Standard does not allow you to inspect page elements to see their individual properties; that's a feature of Acrobat Pro.

                                 

                                 

                                So, if I understand you correctly:

                                 

                                • when I scan one page of paper, the resulting PDF has multiple elements

                                 

                                • one of these elements is an image of that page of paper (assuming no ClearScan or other processing after scanning)

                                 

                                • although this image (stored as an element) has a dpi, Adobe 9 Standard doesn't let me see the value of this dpi or change the dpi (downsample it)