Technology

Screen Resolution and Pixel Density in Modern Displays

The shift to high pixel density screens that started with smartphones and tablets has spread to computer monitors. 4K PC screens have emerged over the last decade and pixel density has become a key factor in product selection alongside display size and resolution. Our theme is the transition to high pixel density screens, including the latest technology trends. There are two standards for 4K resolution, “DCI 4K” and “UHD 4K”.

DPI (dots per inch) is the number of dots that fall within the 1-inch line for scanning or printing. For monitors and displays, DPI is discarded in favor of PPI (pixels per inch). Although PPI is an accurate term for monitors and other screens the two terms are often used interchangeably.

In the light of changing relationship between screen resolution and pixel density of given display, question of what is my screen resolution became more complex to answer than one would assume at first, which lead to invention of the term – Device Pixel Ratio.

Number of device pixels that make up CSS pixels in one direction is the Device Pixel Ratio (DPR). You can interpret this as the width (or height) of the device (physical) pixels that can fit in one CSS pixel. Each device has a different DPR. Higher resolution devices have higher DPRs. These screens can display sharper images because they allocate more physical pixels to each CSS pixel. This means that if a web browser (or other application) naively assumes that pixels are the same as pixels on the screen according to the application’s concept of pixels, then eventually text and images will become so small that they are not easy to see.

The reason behind the introduction of CSS device pixel ratio is that cell phone screens are getting higher resolution and web pages would be displayed too small if every device still had a CSS pixel ratio of 1.

High pixel density or retina monitors sold by Apple typically have a physical pixel density greater than 200 pixels per inch (PPI). This means they have twice the pixel density of PC monitors with classic resolutions. Contemporary smartphones and tablets are the main drivers of this trend due to their low cost and high pixel density, usually above 250 PPI. This means that the average person cannot see individual pixels on a high pixel density screen from 10 to 15 inches away on a smartphone or tablet, or more than 20 inches away on a laptop or computer screen.

4K PC monitors entered the markets in last 10 years and knowing pixel density is becoming important in product selection alongside screen size and resolution. 4K is set to replace Full HD as the standard resolution. 4K, of course, stands for 4000 and refers to the number of pixels horizontally around that number.

DCI 4K has twice the screen resolution of 2048 x 1080 pixels for projectors (4096 x 2160 / approx. 17:9) and is the 4K resolution in the industry. UHD 4K (also called UHDTV 4K), on the other hand, is the television industry’s 4K resolution as defined by the International Telecommunication Union (ITU). It has twice the horizontal resolution of 1920 x 1080 pixels Full HD (3840 x 2160/16:9).

Since the second half of the 2000s, square screens with 5:4 and 4:3 aspect ratios have declined in the PC market, while widescreen 16:9 and 16:10 have gained popularity. At the same time, there is a shift from 17″ and 19″ square screens to 23″ and 24″ wide screens. There is also an active trend towards 27″ or larger widescreen displays for a more comfortable environment. This transition is divided into those looking for a larger work surface with 3840 x 2160 pixels (UHD 4K) or 2560 x 1440 pixels (WQHD), and those who are looking for a screen with better visibility at a lower price, choose 1920 x 1080 pixels (Full HD). In recent years, ultra wide screen products with wider screens have also appeared. These are products with super wide screens and 21:9 aspect ratio.

The world of 8K displays that followed 4K and 5K are also becoming more represented in markets. The 8K (7680 x 4320 pixels / 16:9) compatible test model appears at video shows and events, and the transition to higher definition and higher definition will continue rapidly. When it comes to standalone monitors, 4K monitors with super high pixel densities and screen sizes ranging from 24 to 27 inches have become a hot topic these days. Initially, this genre only attracted the attention of a few high-end users, but gradually cheap products began to appear on the shelves, so that the interest of ordinary users increased.

Computer monitors are based on the assumption that the operating system and applications have a fixed screen density (96 ppi for Windows). Behind this assumption is the 96 dpi standard and screen size increases with higher resolution LCD panels (higher pixel count), so it’s easy to assume that the higher the resolution (pixel count), the larger the work area.

PPI stands for “pixels per inch” (not per square inch). One inch is equal to 2.54 centimeters. If you reduce the pixel pitch without changing the screen size of the LCD screen, the ppi value increases, and the higher this value, the higher the screen resolution. For example, 100 ppi packs 100 pixels by 2.54 centimeters and 300 ppi packs 300 pixels into the same width. Pixels and dots, and also ppi and dpi, are interchangeable terms. However, it is useful to keep them separate when calculating how many pixels it will take to print an image of a certain size on a printer at a certain dpi resolution.

While a higher PPI is always better in theory, before you buy, be aware that most people’s eyes probably won’t be able to tell the difference in a PPI over a certain value.

Going forward, when choosing an display device you will also need to consider pixel density, which is a combination of screen size and resolution. As mentioned before very high pixel density displays generally require zooming, so high resolution (high pixel count) does not equate to large workspaces. This is an important point that should be considered carefully.

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