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I want to shoot a few photos using the smartphone. I will receive JPEG files with a pixel density of 72 ppi. I will then move these photos to my computer and convert them from JPEG to TIFF (using GIMP, ImageMagick or something else).

During editing I don't want to use JPEG because JPEG has lossy compression. It affects on editing and artifacts. If I will edit photos I will save them a few times. If I do this with JPEGs, I will receive artifacts in it which I don't want; so I'll convert the photos from JPEG to TIFF.

In the next step I will edit these TIFFs: some of them I will crop, scale, rotate. In some photos I will adjust brightness and contrast (using GIMP, ImageMagick or something else).

I will then import the edited TIFFs to some software (LibreOffice Writer, Scribus or something else) in which I will arrange photos on pages and add few lines of text to each of them - explanation what is on the photo. On every page, I will arrange a few photos and text to each of them. I will have approximately 9 or 10 pages. I will then convert this file to PDF.

I will send this PDF file to a friend who will read it on smartphone or desktop computer using Adobe Acrobat Reader or something equivalent. Maybe he will want to print this PDF. In this case, the printed photos should not have pixelated, jagged edges.

What PPI I need to set for photos to avoid pixelated, jagged edges on paper?

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    This might be as much about the quality and current settings of the end user's application used to display PDFs as it is about the images embedded within the PDF. – Michael C May 8 at 19:00
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Usually, it is recommended to print photos at 300dpi (= dots per inch, which is the print equivalent to ppi, as printer cannot print pixels but dots). However, if you simply set the pixel density to 300dpi, it might not change anything if the original photo isn't large enough.

You can determine the maximum print size at 300dpi from the photo's dimensions. Let's say your photos have a resolution of 24mp (6000 x 4000 pixels). 6000/300 = 20. This means the maximum width of the prited photo is 20 inches or about 50cm.

Considering you have 9-10 images per page (which I assume is DINA4), even a very low-resolution photo should be big enough to be printed at 300dpi.

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  • Thank you, Jonas, for editing my question and thank you for your answer. Yes, size of page is A4. Width 210 mm, height 297 mm. Size of JPEGs from smartfon are 3328 x 1872 pixels (6.23 MPixels) (16:9). I counted. It will be normal. Yes? – Konskoo May 8 at 8:31
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    @Konskoo yes, the image size is totally fine. You could print them as large as ~11x6.3 inches (28x15.8 cm) which is around the size of a full horizontal A4 paper. – Jonas May 8 at 8:50
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    @Konskoo you can do that in Gimp; here's a link how to do it: guides.lib.umich.edu/c.php?g=282942&p=1888164 however, it is really not necessary to do so before printing as it will have no effect about the actual resolution of the image – Jonas May 8 at 10:44
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    @Konskoo yes, that seems to be good. Enjoy the process! – Jonas May 8 at 17:47
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    @Konskoo TIFF files are lossless. However converting Jpeg to TIFF won't enhance the quality of the JPEGs because in some cases there just isn't data. – Jonas May 8 at 18:26
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Your phone will not generate images with a pixel density of 72ppi... it will generate images with x/y pixel dimensions. What that means in terms of pixels per inch depends on how large it is printed/displayed. E.g. if you use a phone with a 12MP sensor that generates an image of 4000 pixels wide, and you printed that image at 4" wide, it would have a pixel density of 1000ppi (but a printer can't reproduce to that level; and if it could, you wouldn't be able to see it).

The easiest way to determine at what point an image will print pixelated is to enlarge it on your monitor, and then divide that size by the monitor's resolution. E.g. if a 4000 pixel wide image appears pixelated at 200% (2x) zoom that would equate to 8000 pixels wide (2x4000). And if your monitor is running at 102ppi (e.g. 15" MBP at 1440x900) that equates to a 78" wide print (8000÷102); and 4000p÷78"=51ppi. Which is also the monitor resolution divided by the magnification in terms of PPI (102÷2=51ppi)... a ~51ppi 78" wide print would show pixelation in this example.

That's not to say it would be the highest quality print if you printed it at 100ppi instead; but it wouldn't print pixelated (apparent square pixels/jagged edges).

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