DPI settings affects document size

[davorin]

Hello

I assume the DPI settings in the document setup is meant for rendering place bitmap images when exporting.

But why does changing the DPI settings influence the document size itself? It is a vector program after all (o;

If setup a document to be 85mm x 54mm in size with default 300dpi, then changing it to 600dpi the document is enlarged with the graphic elements being scaled down.

[R C-R]

If you have not already seen it, you might want to watch the Affinity Photo - Understanding DPI video tutorial for some background info on the relationship between image size & DPI. (I am assuming from your "vector program" comment that you are using Affinity Designer, but the video applies equally well to both Affinity apps.)

Aside from that, placed images can & often do have different DPI (really PPI if you want to be pedantic about it) values than the document DPI, including different width & height DPI's. 

[davorin]

Well I am not talking about placed images but created vector objects..

Document size A6 landscape (148mm x 105mm @ 300dpi)

Then I draw a square 40mm x 20mm and change then the DPI settings to 400. Now the vector square is 30mm x 15mm in size, which is a total bug in my opinion. Not to mention the odd empty selection in the screenshot (o;

I expect the vector objects to be the same size no matter what DPI settings it is set..

 

[R C-R]

40 minutes ago, davorin said:

Then I draw a square 40mm x 20mm and change then the DPI settings to 400

Assuming you are using Affinity Designer, in the File > Document Setup > Dimensions tab, try setting the "Documents will" option to "Rescale" & then change the DPI from 300 to 400. 

[walt.farrell]

48 minutes ago, davorin said:

Well I am not talking about placed images but created vector objects..

Document size A6 landscape (148mm x 105mm @ 300dpi)

Then I draw a square 40mm x 20mm and change then the DPI settings to 400. Now the vector square is 30mm x 15mm in size, which is a total bug in my opinion. Not to mention the odd empty selection in the screenshot (o;

I expect the vector objects to be the same size no matter what DPI settings it is set..

I cannot explain the odd empty selection.

However, when you modified the document setup you had the choice of keeping objects the same relative size and same placement on the image (Rescale option), or of keeping them the same absolute size (Anchor to Page).

Edit: To put it another way, your objects have a size, determined by their dimension in pixels when you create them. If you change the pixel density, then your choices are to maintain the same appearance (comparing with the overall document) by changing the number of pixels using Rescale, or of keeping the exact same number of pixels using Anchor to Page.

[davorin]

So AD is not a real vector software  but a mix of vector and bitmap like Gravit Designer

That would explain why opening a SVG file the document size is displayed in pixels like 242.4 x 153.1.

This DPI stuff confuses probably many Illustrator users, like reimporting a SVG export of 85mm x 54mm gives back a document size of 20.5mm x 13mm.

[R C-R]

Affinity Designer is "real" vector software, & like with most other contemporary vector apps that includes support for quite a few raster image features. It even supports every raster image feature of its sister app Affinity Photo, although it cannot create or edit all of them.

But that has nothing to do with the dpi/resize issue. It is just that if you change the document DPI you have to tell the app if you want to rescale its contents or anchor them in place, just as @walt.farrell said. It has many features, but reading users' minds is not among them! 

[walt.farrell]

58 minutes ago, davorin said:

This DPI stuff confuses probably many Illustrator users, like reimporting a SVG export of 85mm x 54mm gives back a document size of 20.5mm x 13mm.

If you have an example of that I'd like to see the .afdesign file and the .svg file, so I can understand it better.

But I'd also like to understand what you mean by "reimporting". Do you mean "File->Open", or "File->Place", or are you doing a drag-and-drop operation, or something else?

[Gabe]

Hi all,

The slice export size ( 1x, 2x, 3x, etc) is linked with your document DPI. 1x is considered 72, and so on.

If your document DPI is set to 72, you will have the following for a 100px square

• .5x - 50 x 50
• 1x - 100 x 100
• 2x - 200 x 200
• 3x - 300 x 300

@144 dpi, you're basically working on 2x. So you will have:

• .5x - 25 x 25
• 1x - 50 x 50
• 2x - 100 x 100
• 3x - 150 x 150

@216 dpi, you're working on 3x

• .5x - 16 x 16
• 1x - 33 x 33
• 2x - 66 x 66
• 3x - 100 x 100

I hope this helps. 

Thanks,

Gabe.