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I've got a question regarding exporting PNG files from Ai Illustrator as I'm having troubles getting sharp looking results.

I'm preparing files for Society6 print-on-demand website and aiming to supply them as PNGs so that I can have transparency in my designs.

I'm looking as an example at a file for mugs 4600 x 2000 px PNG at 300 dpi. The artboard is 1104 x 480 px (to factor in that design is exported at 300 dpi).

Here are the steps I'm taking:

  1. Artboard 1104 x 480 px File -> Export -> Export As. PNG / High 300 ppi / Art Optimised (Supersampling) / Transparent

enter image description here

  1. Check the file size and resolution 4601 x 2001 px (I'm ignoring the fact that file size is 1px more), 300 dpi

  2. Open the file in the "Preview" app on Mac. Choose to display it at Actual Size. Getting closer to the screen I still can see the pixelation :( It's especially visible around the question marks.

enter image description here

  1. When I designed the pattern everything was outlined.

I'm not sure what I'm doing wrong here, I'd expect the PNG to be quite sharp given it's exported from Ai Illustrator and all objects have been outlined.

Have you come across this before? Do you know what might be going wrong here?

I would highly appreciate any help with this. Thank you so much for your time. Dasha

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  • Hi. Welcome to GDSE. Your preview appears to be zoomed in, despite what it says the zoom is set to. Do you have some system scaling enabled? Try switching it off. You can't zoom in on a raster image and expect it to look good.
    – Billy Kerr
    Feb 16, 2021 at 13:54
  • DPI is not an actual quality metric the file designed at 4600 x 2000 72 DPI is the exact same image as 4600 x 2000 exported at 300 DPI. So there is no real benefit of exporting it as a 300 dpi imgae. Just a extra convolution in your porcess (especially consediering that PNG does not have a native way to convey DPI values). So your not really doing what you think you are doing.
    – joojaa
    Feb 16, 2021 at 14:13
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    Preview has 2 definitions of "100%" - i.stack.imgur.com/nErab.png
    – Tetsujin
    Feb 16, 2021 at 15:33
  • I would set your art board to 4600x2000 and leave dpi set to screen resolution.
    – Mysterfxit
    Mar 19, 2021 at 5:43

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building on @joojaa comment: your artboard appears to be properly set to 1104 px which will, when printed at 300dpi, result in a 3.6 inch printed dimension (1104px divided by 300). I say "properly" because you mention a coffee cup.

When "exporting to 300" your result is 4600px. This means you are upsampling, which usually adds some "fuzzy." I note that 300/72*1104 is 4600, which indicates that the original artboard is is implicitly 72ppi.

While PNG does support storing the ppi flag as metadata, you only need to ensure that you provide enough pixels such that the px / expected print dpi = the desired print size. This is usually referred to as the effective resolution.

The 300 number is a rule of thumb for print production that assumes a 150 line screen.

As far as super-smooth curves, you are probably looking on screen at something 4 to 5 times large than what it will appear on a coffee mug (i.e. as if under optical magnification). Probably not an issue.

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  • stackoverflow.com/questions/27323561/… has some detailed discussion about PNG and dpi/ppi. Commenter glen randewrs-perhson in that thread is a PNG specification coauthor
    – Yorik
    Feb 16, 2021 at 19:01
  • I had a this kind of discussion on on png at gd and had authors of spec chime in and verify things. So they are definitely out there reading 🤫 Anyway care should be taken, adobe writes the metadata of png's in their own metadata section. And does not read the pHys chunk. So you can have a situation where the physical resolutions are mismatched by a lot.
    – joojaa
    Feb 17, 2021 at 19:51

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