Some smartphones come up with 4096 x 2160 pixels whereas some with 2560 x 1440 pixels display. Some smart phones have HD resolution, whereas some have either QHD or FHD or HD resolution. Despite same resolution, some screens’ display feels way good, whereas some screens’ display are just satisfactory. The game-changer for such vast change is Pixel Per Inch (PPI). Encompassed within this ‘resolution’ category, the size of the screen (in inches), the number of pixels (how much information it can show) and how densely those pixels are packed, is referred to as Pixels Per Inch (PPI). The size of the display determines how many pixels are squeezed into one square inch: that’s the pixels per inch (PPI) figure, also referred to as pixel density.
Having a 1920 x 1080 resolution indicates the number of pixel along horizontal and vertical of the screen, i.e. there’re 1920p and 1080p squeezed along the length and breadth of the screen. But the quality of images and building any applications is determined by how loosely or tightly the pixels are fitted, determined by screen size and screen resolution.
Screen sizes are measured in inches distancing from one corner of the screen to the opposite diagonal corner. Screen resolution is measured by the number of distinguishable pixels that can be displayed in each dimension. PPI is calculated by the screen size and screen resolution with the following algorithm:
1) The square of both numbers in resolution is added
2) The square root of the result of (1) is calculated
3) The result of (2) is divided by the size of screen.
Let’s calculate the PPI of Samsung Galaxy M31 with 6.4” FHD+ display with resolution 2340*1080p.
Following above steps, PPI = ((2340*2340+1080*1080)^0.5)/6.4 = 402
According to APPLE, 300 ppi is the sweet spot; the display will be more than “just-satisfactory”.
Also let’s see the appearance of image with resolution 1920*1080p in the 4” screen and 7” screen.
PPI = ((1920*1920+1080*1080) ^0.5)/4 = 550
Also, PPI = ((1920*1920+1080*1080) ^0.5)/7 = 315.
Thus, it can be concluded that the pixel density decreases with increase in screen size. Thus, a FHD image can feel like QHD image in 4” screen but HD image in 7” screen.
Great article. Thanks,