Smartphone Display Explained: What is PPI, Touch Sampling Rate, Refresh Rate, HDR And More

Smartphones have displays and that is where all the action happens. You want to call someone, tap the screen. You want to order food, tap on the screen to open the app and get it done. Same thing works for hailing cabs as well. You even use it for watching videos or movies on the go. Screen is the hub where most of your computing tasks take place, but how much do we know about its different aspects, its nature and quality. We’ve decided to narrow down these features, the technology for our readers, giving them an in-depth look at what basic things like PPI, refresh rate, and AMOLED panel mean.

WHAT IS PPI

We start our explainer with pixels per inch or as most of us call it, PPI. You might have heard varied definitions for PPI, but in simple words, it is used to measure the closeness of pixels on a mobile screen. It is also worth pointing out that each pixel is viewed as a square if you get a micro view of the screen sometime. So, for instance, if a smartphone’s display offers 300 PPI, it means there are 300 dots per inch, allowing the images and content to appear crisp and sharp for the viewer.

WHAT IS TOUCH SAMPLING RATE

Next up we are going to talk about the touch sampling rate that is available on most smartphones selling in the market these days. As the name suggests, touch sampling rate refers to the number of times a screen can register your touch input in a second. It is measured in Hertz (Hz) on the specifications sheet.

So, every time you touch the screen, and the amount of time taken by the display to render the next frame, is what you would call touch sampling rate. And like in most cases, higher the touch sampling rate, the display offers better user experience. These days you have phones with 180 Hz or even 240 Hz touch sampling rate, which means the display will look for touch input every 180 or 240 seconds, thereby resulting in faster processing on the hardware front.

WHAT IS SCREEN REFRESH RATE

Another widely popular term these days is screen refresh rate. And no, it is not the same as touch sampling rate as many assume. The term itself explains the technology behind it. Screen refresh rate refers to the number of times the screen refreshes every second. It can be either while you scroll through apps or open an image/visual on the display. Again, higher the refresh rate, the better the screen responds to any task. High refresh rate of the screen is beneficial in many ways. Mostly because they skip a frame, which is ideal for gamers, and even regular navigation on the phone becomes smoother, or fluid as some brands call it.

WHAT ARE THE TYPES OF DISPLAY PANEL

There are four types of display panel that are recognised and used by smartphone makers right now. These are:

TFT Panel

The Thin Film Transistor panel is how we started using smartphones. This technology offers good image quality and supports higher screen resolution. But the biggest issue with TFT panels is the low visibility under direct sunlight, which has prompted brands to look at other options.

IPS Display

Next one is called In-place switching panel, which is basically the upgraded variant of TFTs and focuses on lower power consumption that automatically improves the phone’s battery life. These are costlier than TFT panels, which is why you mostly get them on phones costing above Rs 10,000 in the market. You get good wide viewing angles with IPS panels.

AMOLED Screen

Everyone is familiar with the Active-Matrix Organic Light-Emitting Diode or AMOLED panel that is available on mid-range and high-end smartphones these days. This panel is renowned for its top-notch colour reproduction, and allows phone makers to design lightweight devices. The high brightness level does not compromise on battery life, which is important.

Super AMOLED Screen

This version of AMOLED comes from Samsung. The most intriguing part about Super AMOLED is that the touch sensors are integrated into the main display, which gives you a thin display profile. Samsung now offers this panel for other manufacturers in the market.

OLED Screen

And finally you have OLED or Organic Light Emitting Diode panel. OLED display operates on its own and does not need a backlight to throw visible light. This technology allows OLED to offer deeper blacks and support ultra-thin form factors, be it TV or smartphones. Much like AMOLED, these also offer efficiency which results in better battery life.

Different screen resolutions for smartphones

There are quite a few screen resolutions introduced in the industry over the years. But for smartphones we are specifically focusing on the main quality available in the market these days.

High definition (HD)

The most standard resolution offered on smartphones is HD or high definition. Screen with this resolution produces 1280×720 pixels quality.

Full HD

Full HD resolution is the most popular screen resolution that you get on smartphones. Manufacturers have managed to pack the display quality on phones ranging between Rs 10,000 to Rs 80,000. Full HD resolution translates into 1920×1080 pixels quality.

2K or Quad HD

Next up, you have 2K or Quad HD resolution which is yet to become mainstream in the market. Most devices with this screen resolution feature in the high-end segment. The likes of Samsung, OnePlus and Xiaomi among others have adopted the technology. Screens with this resolution come with 2560×1440 pixels quality.

4K or Ultra HD

And the last known screen resolution available for smartphones is 4K or Ultra HD. 4K screens offer 3840×2160 pixels quality, which is the highest you can get right now, but the options are fairly limited to a few brands.

WHAT IS ASPECT RATIO

You must have heard people write about aspect ratio with regards to display; be it smartphone or television. What does it mean? Aspect ratio is basically the width and the height of the screen of a smartphone. Traditional aspect ratio of smartphones has been 18:9 but with the changing trends in the market, with the adopting of notch and then punch hole layout, now you have 19:9 and 20:9 aspect ratios used for smartphone displays.

WHAT IS HDR

HDR stands for high dynamic range. And any smartphone display which supports HDR stands to offer higher contrast levels than a regular display panel. You also get more colours out of the display while watching movies or any HDR-compliant content. Platforms like YouTube, Netflix and Amazon Prime Video have started offering some of their content in HDR, which can be viewed on smartphones that come with HDR-supported display. And you are sure to notice the difference in quality between regular and HDR content.

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