Difference between the Document (or Layout) DPI and the Raster DPI

[IR_HL]

Hi all

I have a question that is relevant for both Affinity Publisher v2 (just installed) and also v1.10 (which I have kept installed).

Can someone explain to me please the difference between the Document/Layout DPI which you choose when you first create a document (I'll refer to it as the Document DPI from here on out) and the Raster DPI which is part of the export options? I'm only interested in exporting to PDF. I know a resolution that any 'Unsupported properties' will be rasterised at on output needs to be set but I'm unsure which of these settings it is and the relationship between the two.

I'm not really clear why a document resolution needs to be set when a document is created since stuff will only get rasterised on output (where there are rasterisation options). So as you can see I'm confused! I'm coming to AP from Quark and Indesign.

Many thanks,

Iain 

[Old Bruce]

1 minute ago, IR_HL said:

I'm not really clear why a document resolution needs to be set when a document is created ...

It has to do with placing (or 'importing') images. If you place a 256 x 256 pixel image in an 8 inch by 10 inch document that has Null dpi how much space will the image take up?

[IR_HL]

I don't know - the image will have a resolution at a particular size (eg 9cm2 wide at 72dpi or 4.5mm2 at 144dpi). I come from a print background so I am aware of the relationship between resolution and physical size. In Quark/Indesign a document has no resolution - images are placed at a particular size and that defines their resolution on output (ignoring any downsampling that occurs when exported). I am not complaining that AP doesn't work like Indesign but I need to understand how it does work.

[IR_HL]

Does anyone have any further comments? This aspect is quite unintuitive for someone coming from Quark or Indesign. 

If the Document DPI sets what resolution things get rasterised at what does the Raster DPI setting do in the PDF export options?

[Brian_J]

I don't know if the descriptions on the Affinity help page for Above (DPI), Use document resolution, and Use DPI will be helpful to you: 
https://affinity.help/publisher2/en-US.lproj/pages/Publishing/exportSettings.html

I don't understand the need or benefit of all the DPI settings, myself, so my comment is more of a bump to this post... I'm hoping someone can shed light on this topic.

[IR_HL]

Thanks Brian. I have read the help files but am none the wiser. Hopefully someone who knows will come along and help out.

[John Rostron]

I get round this conundrum by:

In any new document I set the dpi to 300.

Before placing any image, I set its dpi to 300 and resize it to the final target size in physical units (mm).

John

[IR_HL]

Thanks John. I'm sure that is wise - in testing I can set my document resolution to a decent number and drop in images of a higher resolution and get them exported at that resolution, which is comforting. But I do like to know all the ins and outs. If possible. 

[Eddy-2]

Publisher 2.04

New document > A4 > 210mm x 297mm > 300DPI

Under Document Setup, I change the DPI from 300 to 200.

When I check the document's size, it's increased to 315mm x 445.5.

????????

[Pšenda]

41 minutes ago, Eddy-2 said:

New document > A4 > 210mm x 297mm > 300DPI

Under Document Setup, I change the DPI from 300 to 200.

When I check the document's size, it's increased to 315mm x 445.5.

????????

210 mm at 300 DPI is 2480.3 px. 2480.3 px at 200 DPI is 315 mm. What do you disagree with about the calculation?

[Eddy-2]

 

6 minutes ago, Pšenda said:

210 mm at 300 DPI is 2480.3 px. 2480.3 px at 200 DPI is 315 mm. What do you disagree with about the calculation?

I don't disagree, simply because, like the author of this post, I don't understand the significance of the DPI setting.

I don't understand why the document size changes rather than just the properties of its contents.

[lepr]

43 minutes ago, Eddy-2 said:

I don't understand why the document size changes rather than just the properties of its contents.

When document unit of measurement is pixel, the physical size should, and does, change when DPI is changed.

When document unit of measurement is physical (such as mm or inch), the physical size should not change when DPI is changed, but a bug in Publisher 2.0 is responsible for the physical size changing.

The bug is fixed in 2.1 beta, and 2.1 retail should be released very soon.

 

[Eddy-2]

4 hours ago, ,,, said:

When document unit of measurement is physical (such as mm or inch), the physical size should not change when DPI is changed, but a bug in Publisher 2.0 is responsible for the physical size changing.

The bug is fixed in 2.1 beta, and 2.1 retail should be released very soon.

Thanks.