How to determine PDF resolution

[colin_ej_clarke@adobeforums.com]

Steve, unfortunately you are incorrect when saying there is no such thing as PDF resolution. There absolutely is. All components of a PDF file may be independant of each other, but if the PDF file is grobally downsampled (photo's, text, etc.) only vector graphics will contain resolution independant data, all other components will be downsampled to the operators request. That's why there's this resolution setting on the FIRST menu in Acrobat Distiller.

The best software to get if you are working with PDF's or a PDF workflow is a third party software made by Enfocus. The software is called Enfocus Pitstop. It allows you to edit PDF's to many many levels. It also allows you to select a graphic and discover it's resolution, any embedded screens, transfer functions, profiles, colour mode etc. You can also change/adjust many of these things, including compression.

[Steve_Werner@adobeforums.com]

The Resolution setting on the General panel of Distiller has very limited utility. Note that it Printer Resolution, NOT Image Resolution. Here is how it's defined in the Acrobat 7 Complete Help:

"Emulates the resolution of a printer for PostScript files that adjust their behavior according to the resolution of the printer they are printing to. For most PostScript files, a higher resolution setting results in larger but higher quality PDF files, while a lower setting results in smaller but lower quality PDF files. Most commonly, resolution determines the number of steps in a gradient or blend. You can enter a value from 72 to 4000. Generally, however, you should leave this at the default setting unless you plan to print the PDF file on a specific printer and you want to emulate the resolution defined in the original PostScript file."

This does NOT affect image resolution. It affects primarily gradients in PostScript files where the smoothness of the gradient is a function of the printer resolution.

[colin_ej_clarke@adobeforums.com]

Steve, my previous post wasn't completely clear (happens when one tries to put a million thoughts into a few words).

Yes, the general tab in acrobat distiller is for Printer resolution, however, all throughout Acrobat there are 'resolution' settings. In the print dialogue box for instance, there is LPI and printer resolution. LPI (Lines per inch) is partially based on Photographic resolution. To output a graphic using a 175 LPI screen, the photo should have a resolution of 350 DPI. Yes it can manufacture a 'fake' line screen at a lower DPI, but the results on press are often dismal and the photo looks muddy. Downsampling - is also resolution based, as seen in the settings (PPI/DPI). Acrobat and Distiller have these options in several areas, and they can be applied to raster images, text etc. As well, when flattening transparancies, which MUST be done somewhere before film or plates can be made (possibly in the RIP) - a DPI (both for the printer and LPI) setting must be used.

From experiences, a low end PDF where graphics are rasterized at 72 DPI, printer resolution is low (ie: 600), and high end compression is used, the PDF will print like someone used a block pencil to create the dots, and gradients have huge areas of banding.

So saying "there is no such thing as pdf resolution", is a false statement, although I do understand why you say it. In the Print industry, resolution is a major factor in determining output and result quality. In other words, I can't print a quality job, if the supplied PDF is low end.

[Aandi_Inston@adobeforums.com]

>So saying "there is no such thing as pdf resolution", is a false statement,

No, I disagree because you've taken it out of context. The statement
"There is really no such thing as "PDF resolution. But a PDF may
contain images with a particular resolution." is exactly right. So
the final results, which depend crucially on resolution, depend on the
resolution of EACH image, which may be different.

You seem to be saying that there are lots of resolutions settings in
Acrobat. I agree with that too, but we are talking about a PDF, not
about settings in Acrobat.

Aandi Inston

[colin_ej_clarke@adobeforums.com]

Aandi, The point I'm trying to make is that there IS resolution involved in PDf's. Drawing straws and separating each element involved in a pdf file is redundant. Just as in Quark, In-Design and other graphic layout programs, elements are separate, but each is resolution dependant.(other than vector - in most cases - not all). For instance, one can have a Quark page with a 72DPI jpg and a 300DPI tif. Sure the page itself will print based on the resolution of the printer and settings, but the 72DPI graphic will print low end - even if the printer is 2400-3000 DPI, regardless. The same is true for PDF files.

The entire point I was trying to make - and I apologize if I didn't word it correctly, was that PDF files - like any other print software, is highly resolution dependant. And I'm using the example of PDF in print media, rather than in other applications. The individual components make up the document, and each component (to a large degree) has areas where the resolution determines it's print quality.

Saying that there is really no such thing as PDF resolution is - in essence true, but also based upon your final usage and many other factors. Breaking the individual elements out of the document is like saying that a cake isn't made out of flower....true, as there are many other elements involved, but also not entirely accurate either.

[Aandi_Inston@adobeforums.com]

We are just agreeing but one last point.

>Saying that there is really no such thing as PDF resolution is

What we really mean is that a PDF has no ONE resolution. So when
someone asks the question "what is the resolution of my PDF" it has no
simple answer, and instead the person asking needs to think about all
of their images.

Aandi Inston

[colin_ej_clarke@adobeforums.com]

Agreed. When I read Lynn's original post, she was asking about how she could tell the resolution of Raster images in her PDF.

[Lyn_Eggleston@adobeforums.com]

Having read all the responses, I wish I had asked my original question as "how can I determine the resolution of the raster images in a PDF" except it would have been too long, but that was what I was asking. Thanks for the interesting discussion.

[Aandi_Inston@adobeforums.com]

Actually, here is another answer. My company sells a plug-in Quite A
Box Of Tricks. It is commercial, but even the free demo includes the
function to click on an image and check its resolution (compression
type, color space...)

That doesn't answer the question for all images, but it does for
single ones.

Aandi Inston

[Doug_Katz@adobeforums.com]

Aandi, in this day and age when images are linked and/or embedded in "container applications" (i.e., vector programs, page layout programs), a PDF isn't the only type of file that has no single resolution, right? What, after all, is the resolution of my AICS2 document that contains type, a few vector graphics, a gradient mesh, and a linked Photoshop file? Isn't the answer the same as what we say about a PDF? And equally accurate? "There's no single resolution."?

[Aandi_Inston@adobeforums.com]

> can't we say that a PDF is not alone in having no single resolution?

Absolutely.


Aandi Inston