PIXEL DENSITY EXPLAINED

One of the less advertised specs of smartphone displays is Pixel Density. Manufacturers would quickly advertise screen sizes, display panel types (LCD or AMOLED) and even refresh rates but would quietly slide the display density somewhere and hope that customers don’t notice. Usually it almost always works.

Read: Smartphone displays


So what is Pixel Density then?

All displays are made of pixels. Pixel density refers to how close together or far apart the pixels on a smartphone’s display are arranged. In other words, if the pixels on your display are packed very close together, that display has a high pixel density. If the pixels are spread apart, then the pixel density is said to be low.

A higher pixel density on a smartphone display means that the user is going to get a lot more detail, sharpness, clarity and resolution in images and videos, better colour representation and contrast. Fonts and lines would look neat and sharp and a better overall image/video quality.

A lower pixel density means less details, less sharpness, possible image pixelation and poorer colour representation. Characters, fonts and lines may not look neat and the overall image/video quality.

Read: Smartphone display resolutions: What they mean and how to understand them.

PPI

Pixel density is measured in Pixels Per Inch (or PPI). PPI simply means the amount of pixels that can be found on an inch (area) of a smartphone’s display.
It can calculated using this formula
PPI = √(screen width2 + screen height2)/screen size

Example:

The Xiaomi Mi A3 has a resolution of 1560 x 720p (HD) and a screen size of 6.09”.
Using our formula:

PPI = √(screen width2 + screen height2)/screen size

PPI = √((720)2 + (1560)2)/6.09 {solve for the squares first}

PPI = √(518,400+2,433,600)/6.09. {add up the numbers in the brackets}

PPI = √(2,952,000)/6.09 {square the number in the bracket}

PPI = 1718.13853/6.09 {divide it by the denominator}

PPI = 282.12


What do the numbers mean?

D class

A pixel density of less than 300ppi can be said to be average. Colours may not be very accurate, detail may be lacking and image quality will definitely suffer. This is particularly seen when resolutions of 720p are used on screens larger than 6”. The pixels are spread too far apart. Examples of devices here include the aforementioned Mi A3 (282ppi), Samsung Galaxy A10 (271ppi), Samsung A20 (268ppi) and Samsung A21 (270ppi). Budget and entry level phones tend to have low PPIs.


C class

Between 300 and 400ppi is a good pixel density to have on a display. Colours are decently represented, details are good and image quality is very okay. Current midrange phones fall within this category because they mostly use 1080p resolutions which is okay for a 6” but you could also find older premium phones here. These include Redmi Note 9S/9 Pro (395ppi), Huawei Mate 30 (389ppi), Xiaomi MI 10 (386ppi), iPhone 11 (323.6ppi) etc.


B class

Pixel densities of 400 to 500ppi are quite impressive. It takes the viewing experience up a notch. Colours pop out, details are sharp and image quality is very good. Midrangers, flagship killers and older flaghips can be found here as well as some new flagship models. Example are Honor 10 lite (415ppi), Redmi Note 7 and Redmi Note 8 (409ppi), iPhone X (458ppi), iPhone 12 (460ppi) etc.


A class

Pixel densities above 500ppi are top of line. You get the best of everything here. Image quality is so good that they seen to jump out of your screen. Details are crisp and the colours are rich and vibrant. Only flagships get to enjoy this kinds of PPIs as the displays around here are mostly 1440p (QHD or 2K) and 2160p (UHD or 4K). Phones here include Samsung Galaxy S20 (563ppi), S20 Plus (525ppi), S20 Ultra (511ppi), Xiaomi MI 11 (515ppi) etc


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