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A designer told me that he makes a design for iOS using 326dpi resolution. If he uses less, they will not look nice on iPhone and iPad screens (image blurry).

On Android, dpi value on the largest resolution is 518. In the past, I have tested exporting images from 72dpi and from 300dpi PSD files, and there was no difference on the screen. I never noticed blurry images. They were all perfect if I had exported them from the exact size of the device screen.

A few years ago, I searched on StackExchange sites an answer to this question, and I found a good article describing that dpi matters ONLY if we will print the design on the paper. For devices, it does not matter.

I lived by that rule for the last few years, but now I am completely confused that dpi started to matter.

Can anyone update me on the dpi issue? Can we create 72dpi designs for Android screens? Do we have to create 326dpi designs for iOS screens?

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    The designer is talking nonsense. PPI makes no difference at all (assuming the same pixel dimension). The only thing that matters is pixel size. – Cai May 27 '16 at 11:31
  • @Cai What do you mean by this? If we use design that has the same pixels as aiming screen, we can use 72dpi or 300dpi PSD file without getting blurry images on the screen? So Retina screen will not display blurry image if it's 72dpi? – sandalone May 27 '16 at 11:51
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    exactly that. A 100x100 pixel image at 72ppi is exactly the same as a 100x100 pixel image at 300ppi. – Cai May 27 '16 at 12:11
  • @Cai This is the same I learned a few years ago. – sandalone May 27 '16 at 12:19
  • the difference is what size software tinks physical units such as font points are. On illsutrator it matters in way that pixels are allways intended to be 72 when using pixel preview – joojaa May 27 '16 at 13:32
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Assuming the same pixel dimensions, PPI (or DPI, but it really is PPI) makes no difference at all.

A 100x100 pixel image at 72PPI is exactly the same as a 100x100 pixel image at 300PPI. No difference at all.

All that PPI value is is a meta tag describing what physical dimensions the image should be. If you are printing your image it matters because it affects the physical size regardless of the number of pixels. Theoretically there could be a system that uses your digital images at a physical size on screen using PPI instead of pixels, but that isn't what happens.

On screen your images are shown at their pixel size, simple as that. High pixel density (e.g Retina) screens confuse that matter slightly but they do not use any PPI value your image has.

If you're using physical dimensions to describe your image then PPI absolutely does matter. A 2x2" image at 72PPI is a lot smaller (in pixels) than a 2x2" image at 300PPI, but there is absolutely no reason at all to be designing images destined for a screen using physical dimensions.

  • I may just start saving my assets at 1 PPI just to prove a point... – Cai May 27 '16 at 12:49

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