DPI significance in document setup

[David Green]

In Affinity Publisher, what exact affect does the 'DPI' setting do in document setup? The help text is too vague, and says nothing about how this setting is used by Publisher and how it interacts with the resolution in generated files:
"DPI—Sets the resolution of your document. For example, for professional print quality, set your resolution to 300 dpi or above."

If I initially set the 'DPI' setting to a low value, will it prevent me generating high-res PDFs? If not, what purpose does it serve?

Perhaps DPI 

I've been using Serif PagePlus for years, and I'm used to only controlling DPI in the files which I generate, like in PDFs, not in the source file.

[Dan C]

Hi David Green

The DPI of the document technically doesn't matter until the document is exported, as it is this time the DPI is embedded into the document and cannot be changed easily. 

The DPI setting will control any pixel data in the document, whilst you're still working on the file in Affinity publisher you can change this DPI on the fly, and any pixel data already in the document will be resampled to match this new value.

On 6/22/2019 at 12:28 PM, David Green said:

If I initially set the 'DPI' setting to a low value, will it prevent me generating high-res PDFs?

It will not prevent you from this, as the DPI can be changed at any time, should you wish.

Certain users require a set DPI for their projects, depending on what they're doing with the file. I expect most files in Publisher to be created at 300DPI and above, but we like to offer this option so we can suit any workflow.

On 6/22/2019 at 12:28 PM, David Green said:

If not, what purpose does it serve?

Certain documents will use a lower DPI for images to reduce the file size when exported (such as serving the file over the web), the lower the DPI, the less information raster images can carry and therefore they have a smaller file size. I hope this helps!

[Carlsson]

I came here to understand this as well. I’ve just started to create my first document in Affinity Publisher (been an Indesign user), and this is the first thing I’d like to know more about.

I’m creating a folder that will be printed on a 1200 dpi digital press later. I will have technical scans containing black lines against white background, I have scanned them in 600 and 1200 dpi to maintain the “crispness”.

 

- Should the DPI setting be 1200?

- What happens if I change this later?

- Could I adjust the DPI if I do a PDF export and that will adjust accordingly in the PDF file?

- What if I get a document from another user, that didn’t set the DPI correct from the start?

- Will all imported pictures be down/upscaled to the current documents DPI?

- What if I have imported a file while the document was set with 300 DPI, and later adjusted the DPI to 1200, will the photo relink to adjust accordingly?

 

Some important things to know, that I think you should update in your documentation. It’s important for us that do prints still.

 

However, I am enjoying the trip into Affinity land so far…  

 

[lacerto]

Obsolete.

[thomaso]

5 hours ago, Carlsson said:

- What if I have imported a file while the document was set with 300 DPI, and later adjusted the DPI to 1200, will the photo relink to adjust accordingly?

In this example I placed an image + copied it twice, at a document resolution of 600 dpi. Then I switched the document to 60 DPI, the visual dimensions of the placed objects did not change. (but if I now click-place the same image once more it would get placed in 10x size because it gets placed relative to the document resolution). So far a change of the document DPI does not alter the existing layout content.

But the current document resolution matters when an object gets rasterised. Here the left image was rasterised at 60 dpi document resolution, the right at 6 dpi. Because they all had been placed at 600 dpi in their 100% layout size their resolution gets changed during rasterisation and they appear different.

[Carlsson]

Thanks for the input. I should have mentioned that the scanned documents are scanned in color, not bitmap. 

There really is a difference scanning these in 300, 600 or 1200 dpi in the printed output. Photos usually don't have this problem, but documents with a lot of details etc really shows a difference.

So if I have understood this correctly; If I create the documents with a 1200 dpi, and import the scans "as normal", there shouldn't be a problem.

[lacerto]

Obsolete.