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Hi 

What I understand is DPI is related to printing but in Affinity Design I think it have other meanings so what it means ? for example  
why its use 218 DPI for iPhone X and 144 for iPad 11’ when creating new documents based on those templates ?even the iOS UI kit offered by Affinity their elements won't have the correct sizes in iOS Guide ?
 
Kindest Regards
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49 minutes ago, Ammar said:

218 DPI for iPhone X and 144 for iPad 11’

I do believe that is the pixel density, the actual number of physical pixels making up the screen.

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Affinity Designer 2.4.0 | Affinity Photo 2.4.0 | Affinity Publisher 2.4.0 | Beta versions as they appear.

I have never mastered color management, period, so I cannot help with that.

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On 4/12/2022 at 5:45 PM, Old Bruce said:

I do believe that is the pixel density, the actual number of physical pixels making up the screen.

I made some calculations and what you said is correct using 216 DPI provide the correct size when converting between points and pixels, now the confusing thing is that in Apple iPhone 13 Pro page it says that iPhone 13 Pro has a 460 PPI not 216 !

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On 4/12/2022 at 6:14 PM, thomaso said:

... while the pixel density together with the image size result in the physical dimensions of 1 pixel … and vice versa.

https://affinityspotlight.com/article/understanding-dpi/

Ok now when I open an image info on my Mac I don't see a DPI or PPI info in meta data and in the link you sent it says it effect the image size say inserted in a publishing software say like Apple Pages App. shouldn't this info be in meta data ?

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44 minutes ago, Ammar said:

I don't see a DPI or PPI info in meta data (...) shouldn't this info be in meta data ?

It can be stored in the meta data but doesn't have to. For the image appearance in a layout only two of possibly three info are required. Even, just the image dimensions (its total x / y pixels) are sufficient to define a certain size on a screen. Then the screen resolution (the monitors hardware pixel size & density) defines the physical size of the image. Lets say you have an image with 1000 pixel width and a screen of 1000 pixel width then the image fills the entire screen width – note this doesn't tell anything about the physical size of the screen and the image and also doesn't talk about dpi yet. On an old monitor with 72 dpi this image would appear in a larger physical size (e.g. mm or inch) than on an iPad with e.g. 144 dpi or a smart phone with e.g. 400 dpi – but the image can get displayed on each of this screens with its full 1000 pixels width (while it would be reduced on a smaller device, e.g. a smart watch, which might for instance just display every 2nd or 5th pixel of this image and thus, of course, show less of the actually existing image details).

Now, if an app gets involved, the app itself can handle the dpi: In Affinity every document must have a certain resolution (dpi). This document resolution influences the size of the placed content. If you create an .afpub with 300 dpi a placed image will appear in a different physical size (mm or inch) than if you place the same image in a 100 dpi .afpub. – Apple's Preview.app doesn't require a certain dpi for its documents. Different to APub in Preview you can't create an empty document without content, Preview takes the dpi from the content it opens and displays. If an image has its own dpi stored then Preview will consider this for the physically displayed size, if not it will scale the image according to the size of the document window: increasing the window (dragging a corner) will enlarge the image appearance.

1 hour ago, Ammar said:

when I open an image info on my Mac I don't see a DPI or PPI info in meta data

The macOS file info panel doesn't mention dpi, but Preview does in its info panel. If you open in Preview an image which has no dpi stored then Preview reports "72 dpi", while for instance the EXIFtool (https://www.exiftool.org/) would report for the same image the resolution "1" + the unit "None". This indicates the low importance of the dpi in an image – very different to its total pixel dimensions.

Note, vector documents (e.g. a text document or a PDF) don't need to have a resolution (dpi) but usually have only physical, absolute dimensions stored (font size, image size, page size). The fact that Affinity layout apps (AD, APub) require a dpi decision from the user is caused by the fact that they work quite flexible and may switch a certain content type from vector to pixel (by rasterization). For this it's helpful to have a certain dpi specified for the entire document which kind of ensures for pixel content a certain "quality" (e.g. smooth antialiasing and sharpness instead of jaggyness).

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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40 minutes ago, thomaso said:

It can be stored in the meta data but doesn't have to. For the image appearance in a layout only two of possibly three info are required. Even, just the image dimensions (its total x / y pixels) are sufficient to define a certain size on a screen. Then the screen resolution (the monitors hardware pixel size & density) defines the physical size of the image. Lets say you have an image with 1000 pixel width and a screen of 1000 pixel width then the image fills the entire screen width – note this doesn't tell anything about the physical size of the screen and the image and also doesn't talk about dpi yet. On an old monitor with 72 dpi this image would appear in a larger physical size (e.g. mm or inch) than on an iPad with e.g. 144 dpi or a smart phone with e.g. 400 dpi – but the image can get displayed on each of this screens with its full 1000 pixels width (while it would be reduced on a smaller device, e.g. a smart watch, which might for instance just display every 2nd or 5th pixel of this image and thus, of course, show less of the actually existing image details).

Now, if an app gets involved, the app itself can handle the dpi: In Affinity every document must have a certain resolution (dpi). This document resolution influences the size of the placed content. If you create an .afpub with 300 dpi a placed image will appear in a different physical size (mm or inch) than if you place the same image in a 100 dpi .afpub. – Apple's Preview.app doesn't require a certain dpi for its documents. Different to APub in Preview you can't create an empty document without content, Preview takes the dpi from the content it opens and displays. If an image has its own dpi stored then Preview will consider this for the physically displayed size, if not it will scale the image according to the size of the document window: increasing the window (dragging a corner) will enlarge the image appearance.

The macOS file info panel doesn't mention dpi, but Preview does in its info panel. If you open in Preview an image which has no dpi stored then Preview reports "72 dpi", while for instance the EXIFtool (https://www.exiftool.org/) would report for the same image the resolution "1" + the unit "None". This indicates the low importance of the dpi in an image – very different to its total pixel dimensions.

Note, vector documents (e.g. a text document or a PDF) don't need to have a resolution (dpi) but usually have only physical, absolute dimensions stored (font size, image size, page size). The fact that Affinity layout apps (AD, APub) require a dpi decision from the user is caused by the fact that they work quite flexible and may switch a certain content type from vector to pixel (by rasterization). For this it's helpful to have a certain dpi specified for the entire document which kind of ensures for pixel content a certain "quality" (e.g. smooth antialiasing and sharpness instead of jaggyness).

Thank you very much for this detailed replay I really appreciate it, kindest regards.

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59 minutes ago, thomaso said:

It can be stored in the meta data but doesn't have to. For the image appearance in a layout only two of possibly three info are required. Even, just the image dimensions (its total x / y pixels) are sufficient to define a certain size on a screen. Then the screen resolution (the monitors hardware pixel size & density) defines the physical size of the image. Lets say you have an image with 1000 pixel width and a screen of 1000 pixel width then the image fills the entire screen width – note this doesn't tell anything about the physical size of the screen and the image and also doesn't talk about dpi yet. On an old monitor with 72 dpi this image would appear in a larger physical size (e.g. mm or inch) than on an iPad with e.g. 144 dpi or a smart phone with e.g. 400 dpi – but the image can get displayed on each of this screens with its full 1000 pixels width (while it would be reduced on a smaller device, e.g. a smart watch, which might for instance just display every 2nd or 5th pixel of this image and thus, of course, show less of the actually existing image details).

Now, if an app gets involved, the app itself can handle the dpi: In Affinity every document must have a certain resolution (dpi). This document resolution influences the size of the placed content. If you create an .afpub with 300 dpi a placed image will appear in a different physical size (mm or inch) than if you place the same image in a 100 dpi .afpub. – Apple's Preview.app doesn't require a certain dpi for its documents. Different to APub in Preview you can't create an empty document without content, Preview takes the dpi from the content it opens and displays. If an image has its own dpi stored then Preview will consider this for the physically displayed size, if not it will scale the image according to the size of the document window: increasing the window (dragging a corner) will enlarge the image appearance.

The macOS file info panel doesn't mention dpi, but Preview does in its info panel. If you open in Preview an image which has no dpi stored then Preview reports "72 dpi", while for instance the EXIFtool (https://www.exiftool.org/) would report for the same image the resolution "1" + the unit "None". This indicates the low importance of the dpi in an image – very different to its total pixel dimensions.

Note, vector documents (e.g. a text document or a PDF) don't need to have a resolution (dpi) but usually have only physical, absolute dimensions stored (font size, image size, page size). The fact that Affinity layout apps (AD, APub) require a dpi decision from the user is caused by the fact that they work quite flexible and may switch a certain content type from vector to pixel (by rasterization). For this it's helpful to have a certain dpi specified for the entire document which kind of ensures for pixel content a certain "quality" (e.g. smooth antialiasing and sharpness instead of jaggyness).

Ok I have a question, now font sizes say for example Title size is 34pt how that is translated to pixels ? As size 18 will have different physical size on different screens such as Mac, iPhone ? And regarding the preview App why it stretches the image without DPI info and not freezing the stretch after passing it’s pixel size ?

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2 hours ago, Ammar said:

Ok I have a question, now font sizes say for example Title size is 34pt how that is translated to pixels ? As size 18 will have different physical size on different screens such as Mac, iPhone ? And regarding the preview App why it stretches the image without DPI info and not freezing the stretch after passing it’s pixel size ?

Hi,

  1. 3 point equals 4 pixel (by convdntion / tradition)
  2. if devices render files at files DPI, yes.  But apps today tend to display files zoomed (in booth ways), it normally differs unless you ask them to display at 100% zoom. Smartphone screens are to small (vs. PC), so zooming out is technically required and unavoidable.
  3. To make files readable. E.g. an PDF containing a A4 page (21x29cm) must be zoomed out to fit on a 8x4cm smartphone screen. User can then zoom in if he wants to
  4.  

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5 hours ago, NotMyFault said:

Hi,

  1. 3 point equals 4 pixel (by convdntion / tradition)
  2. if devices render files at files DPI, yes.  But apps today tend to display files zoomed (in booth ways), it normally differs unless you ask them to display at 100% zoom. Smartphone screens are to small (vs. PC), so zooming out is technically required and unavoidable.
  3. To make files readable. E.g. an PDF containing a A4 page (21x29cm) must be zoomed out to fit on a 8x4cm smartphone screen. User can then zoom in if he wants to
  4.  

Thank you very much.

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6 hours ago, NotMyFault said:

3 point equals 4 pixel (by convention / tradition)

I think the old Mac display standard was 72 dots/pixels per inch, but Windows standard resolution was traditionally 96 dots/pixels per inch. There are 72 points per inch, so 72 points equals 96 pixels (and therefore 3 points equals 4 pixels). 

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55 minutes ago, Alfred said:

I think the old Mac display standard was 72 dots/pixels per inch, but Windows standard resolution was traditionally 96 dots/pixels per inch. There are 72 points per inch, so 72 points equals 96 pixels (and therefore 3 points equals 4 pixels). 

Thats more confusing what you mean by 72 dots/pixels dots are for printers not screens ? now regarding the numbers you mentioned for Macyou mean its 72 points per inch and 96 pixels per inch thats from the product spec ?

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I doubt that there is still a common PC monitor with 72 dpi these days. The 72 is more of a historical value, but still included alive in the current definition of the ancient, typographical unit 'point'. (whose size, by the way, varied over the years until computers and DTP came along).

When searching for product specs of a new monitor you might find the related value alternatively as pixel size in technical data sheets, e.g. to avoid confusion: While this hardware pixel size is fixed, the monitors resolution (DPI) may change in the user's eyes, influenced by the operating system, the graphic card or a user setting.

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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How do Points relate to Pixels:

You can have any number of Pixels per Inch, you can have only 72 Points per inch.*

Pixels can be any size in inches or mm. They are a concept in software, or they are a tiny fixed area on a device's screen. The fixed area can be any arbitrary size from fractions of an inch to inches, depends on the electronics hardware. Think Jumbotron versus Smart Phone.

*Historically the Point has had different sizes, that is a given. We are talking about today and using Points and Computers.

Mac Pro (Late 2013) Mac OS 12.7.4 
Affinity Designer 2.4.0 | Affinity Photo 2.4.0 | Affinity Publisher 2.4.0 | Beta versions as they appear.

I have never mastered color management, period, so I cannot help with that.

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A pixel is a single square 'picture element' (hence pix-el), i.e. a single dot in your image. A 10x10 image is made up of a set of pixels in a grid 10 wide by 10 high, totaling 100 pixels. The 'point' (pt) on the other hand is a unit of length, commonly used to measure the height of a font, but technically capable of measuring any length. In applications, 1pt is equal to exactly 1/72th of an inch; in traditional print technically 72pt is 0.996264 inches, although I think you'll be forgiven for rounding it up!

How many pixels = 1pt depends on the resolution of your image. If your image is 72ppi (pixels per inch), then one point will equal exactly one pixel.

And then there is/was also the iPhone/iOS related introduction to points (see here), which mobile design deals with in order to handle a certain device's pixel density.

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9 hours ago, v_kyr said:

A pixel is a single square 'picture element' (hence pix-el), i.e. a single dot in your image. A 10x10 image is made up of a set of pixels in a grid 10 wide by 10 high, totaling 100 pixels. The 'point' (pt) on the other hand is a unit of length, commonly used to measure the height of a font, but technically capable of measuring any length. In applications, 1pt is equal to exactly 1/72th of an inch; in traditional print technically 72pt is 0.996264 inches, although I think you'll be forgiven for rounding it up!

How many pixels = 1pt depends on the resolution of your image. If your image is 72ppi (pixels per inch), then one point will equal exactly one pixel.

And then there is/was also the iPhone/iOS related introduction to points (see here), which mobile design deals with in order to handle a certain device's pixel density.

So now iPhones that have different PPI means the size of pixel element in each is different right ? 

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2 minutes ago, Ammar said:

So now iPhones that have different PPI means the size of pixel element in each is different right ? 

Yes, and accordingly their density among themselves. (… loops to the first 3 replies in your thread)

For a comparison you can take a look to the Affinity presets for various Devices (menu File > New…) and click through the different sizes & resolutions set for various devices. (note if comparing their page dimensions: this presets have some set in px, others in pt.)

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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1 hour ago, thomaso said:

Yes, and accordingly their density among themselves. (… loops to the first 3 replies in your thread)

For a comparison you can take a look to the Affinity presets for various Devices (menu File > New…) and click through the different sizes & resolutions set for various devices. (note if comparing their page dimensions: this presets have some set in px, others in pt.)

Things are getting more clear now, so even point sizes is different between devices. ok now when choosing say iPhone X with points dimensions and 216 DPI, translate it to the pixels I get the correct dimensions so what kind of calculation made them guess the right DPI ? 

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21 minutes ago, Ammar said:

what kind of calculation made them guess the right DPI ? 

"guess the right DPI" ? – Their DPI remains the same if you alter the unit, no need to calculate or guess it. The calculation happens for the unit conversion and is based on the 72 dpi mentioned in earlier posts above about the typographical unit "point" / "pt".

In case you mean the different but specific DPI of various devices: I assume the DPI + the device dimensions set in the presets for each device are caused by Serif according to their research in technical specifications of the various devices. (I currently don't see the reason why some are set in px, others in pt)

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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Yes I mean the presets cause if I I change the preset dpi for say iPhone X then changing document units from points to pixels won’t give the correct pixels dimensions, I think it’s some how related to the 3x factor maybe ? 

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10 minutes ago, thomaso said:

"guess the right DPI" ? – Their DPI remains the same if you alter the unit, no need to calculate or guess it. The calculation happens for the unit conversion and is based on the 72 dpi mentioned in earlier posts above about the typographical unit "point" / "pt".

In case you mean the different but specific DPI of various devices: I assume the DPI + the device dimensions set in the presets for each device are caused by Serif according to their research in technical specifications of the various devices. (I currently don't see the reason why some are set in px, others in pt)

The other confusing thing is that preset dpi for iPhone X is 216 while the ppi in its specs is around 458 ! 

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21 minutes ago, Ammar said:

Yes I mean the presets cause if I I change the preset dpi for say iPhone X then changing document units from points to pixels won’t give the correct pixels dimensions, I think it’s some how related to the 3x factor maybe ? 

25 minutes ago, Ammar said:

The other confusing thing is that preset dpi for iPhone X is 216 while the ppi in its specs is around 458 ! 

Ah, this seems to be related to the "Retina" screen technology, and also the reason for the unit "point" instead of "pixel", e.g. because pt allows more 'grades' for calculations (to avoid fractions of hardware pixel).

Maybe this article helps: https://affinityspotlight.com/article/hi-res-iconui-design-can-be-pixel-perfect/

… or, depending on your tasks, maybe this thread (this link leads you directly to a moderators post in the quite long thread):

 

macOS 10.14.6 | MacBookPro Retina 15" | Eizo 27" | Affinity V1

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12 hours ago, thomaso said:

Ah, this seems to be related to the "Retina" screen technology, and also the reason for the unit "point" instead of "pixel", e.g. because pt allows more 'grades' for calculations (to avoid fractions of hardware pixel).

Maybe this article helps: https://affinityspotlight.com/article/hi-res-iconui-design-can-be-pixel-perfect/

… or, depending on your tasks, maybe this thread (this link leads you directly to a moderators post in the quite long thread):

 

Thank you very much.

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