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Ron Shutlar

Pixels per inch and not Dots per inch

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Hello Affinity Photo

Would you please inform me how I can change the document size from Dots per inch to Pixels per inch, as there does not appear to be a drop down box to change this setting. I do not print from my own printer, but send my photographs to a professional printing company, so it is imperative that I change this setting to PPI.

Thank you in anticipation

 

Happy New Year 

 

Ron

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Hi Ron Shutlar,
Welcome to Affinity Forums :)
The control you are looking for is the DPI setting (Dimensions section) when you create a new document in Affinity Photo (File ▸ New). If you want to change the DPI value after the document is created go to menu Document ▸ Resize Document.... There was quite a few discussions about the use of DPI instead of PPI in Affinity apps so please refer to this thread (and linked threads there) for additional information/discussion about the subject. 

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Hello QA/Support

 

I my opinion the DPI reference needs to be removed and PPI inserted instead. I  agree with some of the users of Affinity Photo, it has no place within  the software package. The sooner it is removed the better. No other photo editing software that I have used contains DPI.

Regards

 

Ron

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1 hour ago, Ron Shutlar said:

Hello QA/Support

 

I my opinion the DPI reference needs to be removed and PPI inserted instead. I  agree with some of the users of Affinity Photo, it has no place within  the software package. The sooner it is removed the better. No other photo editing software that I have used contains DPI.

Regards

 

Ron

Why?

Pixels Per Inch is total nonsense for a screen measurement and there are no pixels on paper, only dots. So why use a measurement that is so totally incorrect?

All the other programs are wrong, why do something that is wrong just because everyone else does?


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Hello Affinity Photo

The best way forward is for your company to consult with a Colour Management specialist who will then confirm the correct setting.

 

Regards

Ron

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Guest

Ron is correct, the use of DPI for image pixel size is wrong, wrong, wrong! By incorrectly using DPI in APh only perpetuates the confusion....

Will it be changed? I doubt it ....

Cheers

 

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PPI only makes sense for measurements of physical devices like computer displays because only on them can you measure pixel spacing. Prints do not have pixels, just "dots" that have no direct 1:1 correspondence to document or display pixels, so there are no pixels to measure. Thus, it makes no sense to use PPI for print measurements, or anywhere else there is no clearly defined relationship between pixels & whatever it is you want to measure.


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On 1/2/2019 Guest said:

Ron is correct, the use of DPI for image pixel size is wrong, wrong, wrong!

OK, but what would the right terminology be? There is no specific "pixel size" specified for the digital image metadata in every image file type -- pixels could be any size & they do not even have to have a square aspect ratio.


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27 minutes ago, R C-R said:

OK, but what would the right terminology be? There is no specific "pixel size" specified for the digital image metadata in every image file type -- pixels could be any size & they do not even have to have a square aspect ratio.

That messed my mind up when I first came across it several years ago. But I got over it and don't worry about it. Software takes care of all that stuff behind the scenes. Maybe things per inch should be the new standard. tpi rules! Or when ever you see dpi just make your brain see ppi or vice versa. It is really really easy to do and it doesn't matter.


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From Photo FAQs Answered With Tutorials:

Quote

Q: I really don’t understand DPI and Resolution, what the are the differences, which should I be changing?

A: See Understanding DPI.

They use it in a printing context sense, not for the display context where pixels still remain and are the essential measurement.


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1 minute ago, Old Bruce said:

Maybe things per inch should be the new standard. tpi rules!

For that matter, why do we still use inches, when any linear unit types could be used? Then we could use "tput" or "tplut" as the generic term. But since we are really talking about resolution units, maybe it should be "tpru" or "tplru." 9_9


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2 minutes ago, R C-R said:

For that matter, why do we still use inches, when any linear unit types could be used? Then we could use "tput" or "tplut" as the generic term. But since we are really talking about resolution units, maybe it should be "tpru" or "tplru." 9_9

And once again, only if one defines resolution in a manner to indicate physical pixel units would your post make some sort of sense.

An image has only A pixels x B pixels. That's why it is pixels per inch. That it also has X Resolution, Y Resolution & Resolution Units is not material as those are simply metadata fields.

But you can use millimeters instead of inch...at least if you can find an application that will write that unit into the appropriate fields (likely can be done using Image Magic). But then there may not be any applications that can utilize those fields for their math.


My computer is a nothing-special Toshiba laptop with unremarkable specs running Windows 10 64-bit.

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2 hours ago, MikeW said:

An image has only A pixels x B pixels.

Exactly. The only 'universal' measurement unit is the number of pixels in each dimension of a digital image file. The rest of it is metadata that may or may not be included in the file, & even when it is it may be ignored by the software used to display, edit, or print it.

And of course, depending on the format the file can include a mix of resolution-independent vector objects, multiple raster images with different pixel resolutions, multiple layers or the equivalent defined in several different ways, & text objects that may have no definite form defined within the file itself.

Basically, the file is just a container for abstract virtual objects & data about them that can be manipulated in many different ways by software to create images. There is no one "this per that" metric that makes sense for all of them.


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Would it really be so bad to have both options displayed and changeable?

DPI:     PPI:  

After all, its only a bit of Math and it would kill this perennial argument dead.


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Guest

You can call them ‘sardines’ and ‘rainbows’, it doesn’t matter. It’s about communication and ensuring everyone understands the language. NASA’s Mars Climate Orbiter failed because the wrong units were used - give a printing lab the wrong info and they don’t pick up the error you’ll crash and burn-up.

PPI refers to the pixel resolution of a digital image, DPI refers to the density of ink dots on paper. The nuances of the terminology can be discussed ad infinitum but the bottom line is this is the industry standard. To suggest the terms are ‘interchangeable’ is incorrect and lazy.

The developers should set a good example and use the correct terminology.

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On 1/3/2019 Guest said:

PPI refers to the pixel resolution of a digital image ...

Except that the pixel resolution of vector objects is indeterminate (because they are not defined in terms of pixels), the size of a pixel may be defined indirectly or not at all, & so on. "Pixel" is just a generic term for picture element, & like the generic term "dot" it refers to different things in different contexts.

There is no way any multi-character shorthand term, regardless of what we might agree it stands for, can be "correct" in any meaningful sense in all those contexts.


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6 hours ago, firstdefence said:

Would it really be so bad to have both options displayed and changeable?

Who cares what is the name. For ages professionals have used DPI and it is widely understood. When you are talking about digital pixel image everybody understand that DPI and PPI are used interchangeably. In scanning softwares Hamrick's Vuescan uses DPI, Lasersoft Silverfast uses PPI in user interface but user guides use DPI freely.

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The two terms are used interchangeably because both of them are generic rather than specific, which makes them well suited for use in references to several different technologies, some of which have evolved over time to include things that did not exist when those terms were coined.

The alternative is coining an ever growing number of different terms, each one specific to some clearly defined technical context. I don't think anybody really wants that, not even the most pedantic among us.


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3 minutes ago, >|< said:

Straw man. This thread has never been concerned with vector graphics.

The opening post made the context clear: a digital image composed of pixels being provided to a printing service.

Yes, a printing service that is extremely unlikely to require anything specified in terms of PPI rather than DPI.


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R C-R,

As regards an image, and only an image, if I were helping a user modify an image, what would I call these 4 things outlined in red?

capture-002412.png.0f12900bcea35d86458c8daf799b0530.png

And if I wanted to communicate to that user about the number of pixels in an image, how would I express H/W of an image? Hint:

capture-002413.png.c7b4498d31523ae3f4853101bf2a1a43.png

And what term would I use to express who many of the things (from the first question) fit within an absolute measurement if that image is at 100% size?

Sometimes a pixel is just a pixel.


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10 minutes ago, >|< said:

You think wrong.

Do you think there actually are any people who would be happy about having to contend with what could be a dozen or more different terms ... if they understood that is what it would take to make things "right"?


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