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Should changing the DPI of the document change the size of a document page?


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In Publisher 2.0.3, I have a document with a page size of 100x100mm at 300DPI.
If I then change the DPI to 72 my page is now 416.667x416.667mm.
See attached video – V1 first, then 2.0.3.

This can’t be right, can it?

This doesn’t happen in Publisher V1, nor does it happen in Designer V1 or V2 (haven’t checked Photo).

Am I just doing something silly, or am I missing something important?

(I did a quick search but couldn’t find anything relevant.)

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3 hours ago, MikeTO said:

I agree, this is a bug and is different than v1.

FWIW, I think so too; confirmed on my Mac running Catalina.

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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15 hours ago, GarryP said:

This can’t be right, can it?

Nope.

8 hours ago, MikeTO said:

this is a bug

5 hours ago, R C-R said:

confirmed on my Mac running Catalina

Yep.

MacBookAir 15": MacOS Ventura > Affinity v1, v2, v2 beta // MacBookPro 15" mid-2012: MacOS El Capitan > Affinity v1 / MacOS Catalina > Affinity v1, v2, v2 beta // iPad 8th: iPadOS 16 > Affinity v2

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On 1/26/2023 at 9:12 AM, GarryP said:

This can’t be right, can it?

Yes, this is what I would expect. How are you defining 'size'? The size in pixels does not change. The DPI maps the pixels onto printable  measurements. Change the DPI, and you change the physical measurements. I would expect to see a new measurement of 417mm (100×300/72).

On this basis,V1 was wrong.  When you resized the documents, was Resample ticked?

John

Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC

CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630

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17 minutes ago, John Rostron said:

Yes, this is what I would expect. How are you defining 'size'? The size in pixels does not change. The DPI maps the pixels onto printable  measurements. Change the DPI, and you change the physical measurements. I would expect to see a new measurement of 417mm (100×300/72).

On this basis,V1 was wrong.  When you resized the documents, was Resample ticked?

I believe you're speaking about Photo and this thread is about Publisher. Changing the DPI in Photo should change the document's size but not in Publisher. v1 was correct.

Download a free manual for Publisher 2.4 from this forum - expanded 300-page PDF

My system: Affinity 2.4.0 for macOS Sonoma 14.3.1, MacBook Pro 14" (M1 Pro)

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FWIW, the bug is still there in the new Affinity Publisher for Mac version 2.0.4 released today.

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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37 minutes ago, MikeTO said:

I believe you're speaking about Photo and this thread is about Publisher. Changing the DPI in Photo should change the document's size but not in Publisher. v1 was correct.

I was  writing about Photo, but why would Publisher be different? If you did not want a different document size, then why change the dpi? The current behaviour of V2 seems logical to me.

John

Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC

CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630

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1 hour ago, John Rostron said:

I was  writing about Photo, but why would Publisher be different? If you did not want a different document size, then why change the dpi? The current behaviour of V2 seems logical to me.

Publisher isn't based on pixels like Photo. A photo's actual size is determined by its number of pixels. A 1000x1000 pixel image is the same size regardless of its resolution which is used for placing in other documents and for printing. At 200 dpi, that 1000 pixel image would be 5x5 inches when placed or printed.

Publisher is focused on printing so physical sizes are more important. An A4 or Letter document needs to be that size regardless of whether you're printing at 300, 600, or 1200dpi. Normally with page layout apps you only specify resolution when printing, not when creating or modifying a document or spread. Publisher uses the document or spread resolution to determine how images placed on the spread should be scaled. That 1000x1000 pixel image would be 3.33x3.33 inches when placed without scaling in a 300dpi document but 1.67x1.67 inches in a 600dpi document.

I could be wrong, but I think that's all that the DPI field does and it really isn't important, you're almost certainly going to scale that image to the physical size you require and resolution matters when it comes time to print. Then you'll specify the output resolution for rasterization. The Help system also isn't much help for this field.

Download a free manual for Publisher 2.4 from this forum - expanded 300-page PDF

My system: Affinity 2.4.0 for macOS Sonoma 14.3.1, MacBook Pro 14" (M1 Pro)

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The expected behaviour:

If document units is pixels, changing PPI should not change the quantity of pixels, but the document's physical size should change.

If document units is physical (for example, inches or millimetres), changing PPI should not change the document's physical size, but the quantity of pixels should change.

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3 minutes ago, ,,, said:

If document units is physical (for example, inches or millimetres), changing PPI should not change the document's physical size, but the quantity of pixels should change.

But that is what it seems to be doing in Affinity Publisher V2.

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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16 hours ago, R C-R said:

But that is what it seems to be doing in Affinity Publisher V2.

Not on my computer or the computer of others in this thread.

APub2 (2.0.3 and 2.04 on macOS) is behaving correctly only when document units is pixels.

When units is physical, a change of PPI is wrongly resulting in a change of physical size because the quantity of pixels is not being changed, which is the behaviour expected (and correctly happening) when units is pixels.

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4 minutes ago, ,,, said:

When units is physical, a change of PPI is wrongly resulting in a change of physical size because the quantity of pixels is not being changed, which is the behaviour expected (and correctly happening) when units is pixels.

Isn't that exactly what has been reported here when the APub doc is using mm units, like in the post @GarryP started this topic with?

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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8 minutes ago, ,,, said:

I am in agreement with GarryP and don't understand why you can't stop pestering me.

I'm not trying to pester anybody. I am just confused what you meant in this earlier reply when you said "Not on my computer or the computer of others in this thread." 

That sounded like you were saying that the unexpected resize bug was not happening on your computer.

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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3 hours ago, MikeTO said:

I could be wrong, but I think that's all that the DPI field does and it really isn't important

IMO the primary role that DPI document setting in Publisher (and Designer) had in 1.x versions of Affinity apps was setting the resolution for objects that will be rasterized on canvas (similarly as the "Raster effects" DPI setting in Illustrator). The setting would also determine the default for resolution to be used when needing to rasterize objects when exporting (this can be overridden at export time e.g. in context of PDF export). IMO v2 apps (Publisher and Designer) behave incorrectly when resizing physical dimensions of the document when document DPI is changed. This did not happen with v.1 versions (even when the document unit was px), and I cannot see why this has changed. Personally I see this as an indication of fundamental problems in trying to keep alive the idea of one global workspace and document object model. This seems to be an eternal source of confusion both for developers and users alike.       

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11 minutes ago, lacerto said:

IMO v2 apps (Publisher and Designer) behave incorrectly when resizing physical dimensions of the document when document DPI is changed.

So are we all in agreement that this is a bug in V2?

All 3 1.10.8, & all 3 V23.0 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7
Affinity Photo 
1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7

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4 minutes ago, R C-R said:

So are we all in agreement that this is a bug in V2?

Who knows if this is a regression or an intended change not just been implemented in full? IMO Publisher and Designer kinds of apps should behave differently than fundamentally raster-based apps like Photo, but Serif clearly thinks differently.

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I believe it's a bug that probably crept in when the Document Setup dialog was redesigned for v2.

It's important because changing the DPI shouldn't change the physical size for your book, brochure, or what not, but it's not important because the document DPI really doesn't do anything other than help scale placed pictures. I'd never changed document DPI myself until investigating the reported issue today.

Download a free manual for Publisher 2.4 from this forum - expanded 300-page PDF

My system: Affinity 2.4.0 for macOS Sonoma 14.3.1, MacBook Pro 14" (M1 Pro)

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14 hours ago, MikeTO said:

At 200 dpi, that 1000 pixel image would be 5x5 inches when placed or printed

If we're ok that :

For printing, sizes are often in mm and resolution in DPI (dots per inch)

- For screen, sizes are in pixels and resolution in PPI (pixels per inch)

Should I better read :

"At 200 ppi, that 1000 pixel image would be 5x5 inches when placed or printed" ?

A "dot" is not equal to a "pixel" ; am I correct ?

Talking about PPI, old screens were 72 ppi… and modern ones can be more than 400 ppi (iPhones, iPads, etc…).

And there comes "retina" and I'm a little lost…

 

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14 hours ago, lacerto said:

IMO v2 apps (Publisher and Designer) behave incorrectly when resizing physical dimensions of the document when document DPI is changed.

Designer 2 is OK and the same as v1 - it does not resize physical dimensions when changing DPI of a document with physical document units.

It is Publisher 2 that has changed since v1 and now incorrectly performs physical resizing when changing DPI of a document with physical document units.

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My memory might fail, but I thought you have always the choice to resize canvas, change units, change dpi, or resample document in all 3 apps, but UI is totally different, and especially handling of fractional pixels differs.

 

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