Today, we’ll be discussing all the aspects of display and touchscreen. The mobile phone display has evolved much over the years. Though the first touchscreen mobile, IBM Simon, was released way back in 1992, the technology remained largely unnoticed until 2007, when Apple released the iPhone. Rapid gain in popularity and decrease in manufacturing costs resulted in great advancements in technology, making touchscreens thin, durable, accurate and fast. Also improving in parallel is the display quality. Today’s smartphones render stunning life-like images by packing in tinier and tinier pixels in the screen and coupling it with faster GPUs.
A typical display description of a smartphone will contain the following information:
- Display type
- Touchscreen Type
- Display size
- Screen resolution
- Protective coverings
For example, let us take the Huawei mate 8:
- Type: IPS-NEO LCD capacitive touchscreen, 16M colors
- Size: 6.0 inches (~78.0% screen-to-body ratio)
- Resolution: 1080 x 1920 pixels (~368 PPI pixel density)
- Multi-touch: Yes
- Protection: Corning Gorilla Glass 4
Let us consider these terms one at a time:
There are two major types of touchscreens-
This type is extensively used in ATMs, restaurants, factories, etc. A major advantage is that since these screens respond only to pressure, they can be operated by a stylus or a gloved hand. However, this technology is not popular in the cellphone industry, as the glass used is too thick to offer a good display contrast. Also, since the outer layer of glass is made to touch the inner layer, cracks and dead spots are common. Only a handful of dated phones have resistive screens. These include the Sony Ericsson Xperia x1 & x2, Nokia 5800 XpressMusic, and Samsung Jet.
Projected Capacitive (Pro-Cap)
Almost all modern day smartphones use capacitive touchscreens. This technology utilizes the natural electrical conductance of the human body. It can even be programmed to detect multiple touches. These screens are more durable; and is thin enough to allow most of the light from the display to pass through. Some manufacturers reduce the display thickness even further by doing either of the following:
- Incorporating the touchscreen in the display panel itself (super AMOLED), or
- Incorporating the touchscreen on the protective glass covering.
One major drawback of capacitive screens is its inability to detect touches from insulated material, like a gloved hand.
There are two major display types available in the market: LCD and AMOLED.
LCD (Liquid Crystal Display)
A basic structure of LCD is shown below. It suffices to know that there are two types of LCDs in the market:
Twisted Nematic Thin Film Transistor (TN TFT) LCD: This type has lost popularity over the years due to poor viewing angles and less contrast. Samsung Galaxy J5 Prime, launched last September, features a TFT display.
In-Plane Switching (IPS) LCD: This is the most popular LCD screen, with better contrast, wider viewing angles (compared to TFT) and increased power efficiency.
AMOLED (Active Matrix Organic Light Emitting Diode)
Unlike LCD screen, each pixel is a combination of three to five LEDs (subpixels), which light up separately to produce different colors. As there is no back-light, these screens produce deeper blacks and offer better contrast. The screen also involves fewer layers, reducing the ‘depth’ of the display.
A comparison between the two display types is given below:
|Colour production (gamut)||less||more|
Image quality depends on various factors, including the display type, the GPU, brightness and contrast offered, the glass covering the display, glare filters and even the screen protector you pasted over the screen. However, smartphone companies have decided to advertise on only one factor: screen resolution. The reason behind it is simple, the resolution is an objective quantity, and is easier to explain than glass types, polarized filters, hardware modifications, etc. Nevertheless, the resolution is the most important factor determining display quality.
So what is a screen resolution? It is the number of pixels on the display in both axes, presented in this format: the number of pixels horizontally x number of pixels vertically. What is a pixel? It is the smallest bit of image that your screen can produce.
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Given below are some widely available screen resolutions:
- 720×1280 (HD Ready)
- 1080×1920 (Full HD)
- 1440×2560 (Quad HD/ QHD/ 2K)
- 2160×3840 (Ultra HD/ UHD/ 4K)
Sometimes only the horizontal pixel count is mentioned. For example, 720p screen is another name for HD Ready screen.
Manufacturers have two ways to increase screen resolution:
- Reduce size of individual pixels
- Increase the size of the screen
Hence resolution is not a reliable indicator of sharpness, without taking the screen size into account. It is possible for a 5 inch HD screen to have better image quality than a 6-inch QHD screen. It is, therefore, wiser to look at pixel density, expressed as PPI (pixels per inch). A decent 5 inch HD display will have the pixel density of about 300 ppi, whereas the value can crank up to 800 ppi in premium UHD smartphones (Xperia Z5 Premium for example).
However, during regular use, it is very difficult to appreciate any change in image quality above 400 ppi. At the same time, such ‘ultra’ screens eat into the battery life and affect your device’s overall performance. And if that wasn’t enough, companies might use cheaper hardware elsewhere in the device to compensate for the cost of the screen. It is, therefore, more practical to go for HD or HD-ready screens, which will offer better battery life and faster performance.
A broken screen can result in a broken heart. Manufacturers recognize this and add extra precautions so that your phone can withstand accidental drops and inevitable scratches. Many smartphones now come with something called Gorilla Glass. This is simply a clear, thin, but very tough layer of glass, manufactured by Corning Inc. The toughness comes from replacing Sodium ions with Potassium on the glass surface, through a process called ion exchange. As Potassium is larger than Sodium, the glass becomes more compressed and ‘taut’. Corning claims that the Gorilla Glass 5 can survive 1.6-meter drops on rough surfaces up to 80% of the time, without compromising on clarity and touch sensitivity.
Apart from Gorilla Glass, manufacturers may take additional steps, like a raised bezel to prevent contact between glass and ground. They might also offer scratch resistant plastic guards with their devices. But ultimately, it is up to us to handle our devices responsibly to keep that screen smooth and shiny as ever.