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Many different screens have the same resolution. For instance, both my laptop and phone have resolutions of 1920x1080 pixels.

I'm wondering is there a point where increasing the number of pixels on the screen makes no difference to the our own perception of the screen's clarity or sharpness? Is it necessary for my 5 inch phone screen to have a full HD display or is it possible that it would look just the same if it had some slightly lower resolution?

  • well, when the actual pixel size is too small to be seen by the human eye. keep in mind, the physical dimensions of a pixel are not only the result of the resolution, but also of the screen dimensions. a 55" screen at 1080p will have larger pixels than a 5" screen at the same res. – Frank Thomas Jan 6 '18 at 0:09
  • The relationship of human vision, screen resolution and viewing distance is well understood. See google.com/… – sawdust Jan 7 '18 at 0:41
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Yes. While measurements differ, research (and observation, and logic) all indicate there is a point where our eyes cannot see anything smaller, and this defines the limit of the minimum necessary Pixels Per Inch (PPI) at which we cannot see the individual pixels comprising the image.

1920x1080 is actually quite low-density, even on a 5 inch phone screen. The average eye can easily see individual pixels at this resolution, as this is only about 440ppi.

Personally, I've used a "Quad HD" phone, the LG G3, which had a 5.5 inch screen packing 1440 x 2560 pixels (4 times 720, hence "quad") with a density of 538ppi, and while it was beautifully sharp, I could still see individual pixels with my unaided eye.

Research suggests that beginning around 800ppi is where the eye can no longer detect individual pixels, with some studies indicating the number is closer to 2000ppi. Personally, I'd say the real number is closer to that lower number.

A slightly funny fact regarding all this is that Apple's vaunted "Retina" displays, which were supposed to be so very sharp (they are quite beautiful, but they aren't what they claim to be) are about 220-260ppi, a very low number compared with other high-end mobile device displays.

  • "... this defines the limit of the minimum necessary Pixels Per Inch" -- Using PPI as a metric without a distance qualifier is ridiculous. A reasonable PPI for a handheld tablet would be overkill for a projector screen or full-size HDTV. – sawdust Jan 7 '18 at 0:43
  • That's a good point - in my case, I had been wondering mainly in the context of a laptop display or phone screen where distance would be relatively constant. – screeb Jan 7 '18 at 1:06

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