Did you know your eyes don’t really see the full details in some super high res smartphone screens? Yep it’s true, technology has not only caught up with our eyes but gone beyond what we can perceive. This article will explain PPI, retina display and also touch on the biological limitations of our eye.

Screen basics, the resolution.

The basic spec of a screen is measured in pixels and usually looks something like 1280X720. These numbers describe the number of independent dots that make up the screen; each dot can display a unique color and combined these small dots make up your display. Generally the higher the number of pixels the more detail the screen will show.
If you look really closely to your screen you will be able to see these tiny pixel dots that make up your display, assuming it is not a retina display.

Looking at my PC screen I can easily see the pixels up close.
If I look up close at my PC screen I can easily see the pixels, at a distance it is harder to see each pixel.

Introducing pixel density.

Once you know the pixels in your screen you have the basic understanding. We now need to look at how large your screen is. If the resolution stays the same then the larger the screen the less dense the pixels will be as the pixels are spread across more surface area. PPI mean “pixels per inch” and it calculates the number of pixels in a square inch. The higher the PPI the more sharper the image appears and the closer you can get to the screen and still not notice the pixels.
Density basically means that a 6 inch 720P screen would have a lower PPI then a 5 inch 720P screen. Both screens have the same number of pixels 720P (1280×720) but the 6 inch pixels are larger as they need to fill a larger area. A larger pixel results in a reduction in PPI and sharpness. In terms of sharpness, the actual resolution is not as important as pixel density.

Pixel density is the relationship between total pixels and screen size, as the screen gets smaller the pixels get more dense.
Pixel density is the relationship between total pixels and screen size. As the screen gets smaller the pixels get more dense and therefore PPI increases.

How to calculate PPI

The easy way is to go to this site and enter the screen size and pixel resolution.

My computers PPI, is low compared to a phone, but i view at a further distance so it is less noticeable.
My computers PPI 122 , low compared to a phone, but at a further distance it is less noticeable. Also note the Steve Jobs quote.

What is the best PPI?

The interesting part here is the human eye can only distinguish detail to a certain point. If the display is over 400 PPI then it is considered beyond noticeable. Even up close, screens 400PPI or higher look so sharp, like a real photo or piece of paper as your eyes are not strong enough to see the pixels. Some phones such as the Xiaomi 4 have a PPI of 440 on their 1080P (1920×1080) 5 inch screen, this to some degree, is where marketing has pushed beyond the physical capabilities of the human senses.

Xiaomi 4 packs a screen so good even our eyes cant see the full details.
Xiaomi 4 packs a screen so good even our eyes can’t see the full details.

Even 400 PPI is too high for practical use as how often do you view your screen up close? Realistically a 300PPI smartphone screen at a typical reading distance is far too detailed for your eyes to distinguish individual pixels. Your eyes can not notice the difference between a 300PPI and 400 PPI screen at a normal reading distance.
The only time you would notice the pixels would be if you use VR goggles or 3D glasses that enlarge the screen optically and therefore spread the density.

If you are tossing up a few phones to buy don’t weigh the PPI too high of a decision factor, as long as it is over 300PPI/350PPI it should be sharp enough, your eyes max out at 400 so anything over this is not really significant.

What about Retina displays?

Retina was a term made by Apple to describe exactly what we talked about above, a resolution that when a device is used at its typical operating distance the pixels cannot be detected by your retina. For Apple, 300 PPI or above was labeled a retina display.

 

Hopefully this has opened your eyes to the world of screen density, the limitations of your own biology and also the deeper thought of how technology is advancing beyond what our body can physically sense and enjoy. If you are looking to upgrade your PPI, check out our range of screens packed with the latest pixel density.

 

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  • Stu

    Thanks for the information, the dot story is easily seen with a newspaper, at arm’s length everything looks good, get closer and it all turns to dots.

    I used to be a heavy user of lubricated eyesight. With enough lubrication of my tonsils with the right amount of my favourite brew, everything began to look better, especially the women. I usually found that after too much lubrication the eyesight became more involved with the inside of eyelids than anything else. 🙂 Styoo, Hic!!