All about Phone Screen, PPI, Resolution, Gamut, Gorilla Glass
Greeting MIUIers!
Welcome back to the MIUI Device Classroom . We are back with our second lesson with some of the very important and interesting topics.
In the first lesson prepared by @marcus_keong we have learnt about the specifications which weshould look for when choosing a smartphone. And if you have still not gone through the first lesson just go through it here.
And now in today's class we will learn and uderstand about Phone Screen, the PPI we all used to chant when a new device comes to market, The Resolution of a device which is another important factor while buying a new device, and about the Gorilla Glass. So lets start with Phone Screen.
1. Phone Screen
Mobile phones have progressed a lot since the days we only needed to see the number of person calling us. And when the text messaging facality was added we thought of a bit more space to read what we had writeen. And then came the stage of adding some colours to give mobiles a bit more interest. And then came the stage of adding camras and we were looking for some more sharper screens to see out pixelated VGA photos taken by our device :P
And then we got the ability for watching and storing videos, we wanted them to be smooth and having good refresh rates.
But now times have changed we expect our devices to be as good as our computer screens, offering us with crisp text and some of the vibrant images and also blur-free videos. Outdoor visibility is also one such factor which consumers look for. Here I will explain about different mobile screen types.
TFT-LCD
TFT is Thin Film Transistor technology. The TFT LCDs are one of the most common types fo display that are used across devices. TFT offers a better overall image quality and somehow higher resolutions as compared to earlier versions of LCD displays, but it has narrow viewing angles and poor visibility in direct sunlight. Since it is cheaper to manufacture so you can see it on more number of budget devices and low end smartphones.
IPS-LCD
IPS means In-place Switching. If you start comparing TFT alongside IPS, then IPS is btter display with wider viewing angles and lower power consumption which automatically gives improved battery life. However these are costlier than any normal TFT LCD so you will find this on high end smartphones. One interesting fact is Apple iPhone used a resolution of 640 * 960 pixels version of IPS LCD and they named it as Retina Display because of its brilliant picture quality.
AMOLED
AMOLED is Active Matrix Organic Light Emitting Diode, this technology has grown in recent years, and particulary used by Samsung for its products. This kind of screen consists of a thin layer of organic polymer which lights up when a current is provided to it. These screens are extremely thin, have a simple construction, and don't require any backlight, which saves battery life in phones and tablets.
A PRO TIP:- Just keep the background nearly black and you will save energy :)
Super AMOLED
These are even advanced version of AMOLED displays, again developed by Samsung. These displays are built with touch sensors on the display itself, ending the need of separate touch senstive layer. So this makes it the thinnest diplay tech on the market. They are more responsive than AMOLED dsiplays.
OLED SCREENS
Organic Light Emitting Diode is considered to be better for battery life as it doesnt use any kind of power to create black. These displays produce vivider colors than LCD and are much brighter and has great viewing angles. Touch response is also very good in these displays. As a consumer we need better performace, vivid colors and much brighter screens. So now OLED displays are "best choice". But these have a shorter life span
Benefits of OLED screens:
- Light weight
- Great responsiveness
- Bright and bold colours
- Better definition than most LCD screens
- Very thin
- Less battery hungry in many cases than other screen types
Drawbacks of OLED screens:
- Age quickly and can lose colour clarity for reds and blues
- Expensive, used in high-end smartphones, and are inaccessible to those on a budget
Which Smartphone SCREEN SHOULD YOU CHOOSE?
In real terms it is quite hard to say whaich one is "better" than the others as laterst displays have very good performing screens. Every display type is unique in its own way and here personal choice plays a vital role. One factor that can affect your decision is cost. OLED screens are more costly, and if you have a limited budget you might not consider these. For this main reason most of the affordable smartphones tend to provide LCD screen which provides us best compromise between value and performance.
2. Pixel Per Inch (PPI) and Resolution
Above we have discussed about different displays, and there are two factors namely Resolution and Pxel Density which decides their cost and quality. Here we refer quality as sharpness of the screen to display content.
We must know what a Pixel Is??
In simple language it is a dot on a display or screen, or it is the smallest element that can be displayed on a screen.
Displays are measured in size, but in this case we only measure the diagonal size and not the horzontal or vertical size of screen. Basically resolution refers to size of display in terms of pixels. For example, your device has a resolution of 800 by 600 pixels, means there are actually 800 pixels horizontally and 600 vertically. So it means a total of 480000 pixels in you device display.
Resolution is just the number of pixels on the display and this property alone does not measure the quality of display.
Many of us are not aware of the importance of pixel density in the screens. It tells about the sharpness and clarity of the screen. The pixel density is measured in PPI(Pixel per inch) which tells of number of pixels present in display. The sharpness increases with pixel density. Higher pixel density means more sharper content on screen.
Pixel Density = Root((Horizontal Number of Pixel^2) + (Vertical Number of Pixel^2))/Screen Size
In the above image the Alphate "A" on the left is displayed with lower resolution whereas the one on the right side displayed with higher resolution which delivers better sharpness
The following diagram illustrates the meaning of “pixels per inch”. We’ve considered a hypothetical display that measures 1-inch in each direction. Pixels are shown as a grey square. Starting from the leftmost example, we have a display with just one pixel. The one pixel takes up the entire display. In this example, there’s one pixel for one inch of display. We say the display has a pixel density of 1ppi.
Moving rightwards to the next image, the number of pixels has been doubled in both directions. The pixel density has also doubled to 2ppi. The pattern continues as we move to 4ppi and 8ppi.
As pixel density is increased, the display is able to show more details in an image. The following diagram shows the effect of increasing pixel density. We’ve shown a heart on our one-inch square display. As pixel density is increased to higher ppis, finer details can be seen. The image becomes progressively clear.
A key thing to note is that when pixel density is doubled, the amount of information shown is quadrupled. Taking an example from the diagram above, as we go from 1ppi to 2ppi the pixel density doubles. At the same time, the pixel count quadruples. From 2ppi to 4ppi, we see the same pattern. A doubling of pixel density leads to a quadrupling of pixel count. As we move towards smartphones with a higher pixel density, the amount of information shown increases even faster.
An increased pixel density allows for more deails to be shown. Displays with highe pixel density will give clearer and sharper images
| PPI Range | Quality Perceived |
| 100-150 | Poor |
| 150-200 | Acceptable |
| 200-250 | Good |
| 250-300 | Very good |
| 300-350 | Excellent |
| 350-450 | Eye popping |
| 450+ | Life like |
3. Gamut
Most of the companies nowadays are giving their high end models in market with such great specifications with latest SoC high DPI displays and much more RAM. But one of the most misunderstood parts of smartphone is a display's acuracy.
Many people associate larger gamut with better display quality, but taking this logic to the extreme results in extremely unrealistic colors. The truth, as always, lies somewhere in between. Too large or too small of a gamut makes inaccurate color reproduction. This is where a great deal of the complexity lies, as many people can be confused as to why too large of a display gamut is a bad thing. This certainly isn't helped by marketing, which pushes the idea of greater gamut equating to better display quality.
The most important fact to remember is that all of the mobile OSes are not aware of color space at all. There is no true color management system, so the color displayed is solely based upon a percentage of the maximum saturation that the display exposes to the OS. For a 24-bit color display, this is a range of 0-255 for each of the RGB subpixels. Thus, 255 for all three color channels will yield white, and 0 on all three color channels yields black, and all the combinations of color in between will give the familiar 16.7 million colors value that is cited for a 24-bit display. It's important to note that color depth and color gamut are independent. Color gamut refers to the range of colors that can be displayed, color depth refers to the number of gradations in color that can be displayed.
Reading carefully, it’s obvious that at no point in the past paragraph is there any reference to the distribution of said colors. This is a huge problem, because displays can have different peaks for red, green, and blue. This can cause strange effects, as what appears to be pure blue on one display can be a cyan or turquoise on another display. That’s where standards come in, and that’s why quality of calibration can distinguish one display from another. For mobile displays and PC displays, the standard gamut is sRGB. While there’s plenty to be said of wider color gamuts such as Adobe RGB and Rec. 2020’s color space standards for UHDTV, the vast majority of content simply isn’t made for such wide gamuts. Almost everything assumes sRGB due to its sheer ubiquity.
While it may seem that a display with color gamut larger than sRGB would simply mean that sRGB colors were covered without oversaturation, the OS’ lack of colorspace awareness means that this isn’t true. Because the display is simply given commands for color from 0 to 255, the resulting image would have an extra saturation effect. Assuming that the saturation curve from 0 to 255 is linear, not a single color in the image would actually be the original color intended within the color space, and that’s true even within the color space. This is best exemplified by the saturation sweep test as seen below. Despite the relatively even spacing, many of the saturations aren't correct for a target color space.
Gorilla Glass is the registered trademark of a specialized toughened glass developed and manufactured by Corning, now in its fourth generation designed to be thin, light and damage-resistant. The company designed the glass for our electronic lifestyles. As we carry around computers, tablets, smartphones, MP3 players and other devices, we risk damaging them through everyday use. Corning's Gorilla Glass stands up to abuse with scratch-/impact-resistant qualities. And Corning's approach allows the glass to be incredibly thin, meaning it won't interfere with capacitance touch screens or add significant weight to a device.
What's Corning's secret? What's so special about Gorilla Glass that sets it apart from other kinds of glass? The answer involves incredible temperatures, a special trough, robots and a molten salt bath. The finished product is a thin piece of glass that can withstand a lot of punishment.
Corning takes the silicon dioxide (SiO2) and combines it with other chemicals before melting it down into a glass melt. The resulting glass is aluminosilicate -- that means the glass contains aluminum, silicon and oxygen. The glass also contains sodium (Na) ions, which becomes important in the next phase of manufacturing.
Corning pours the molten glass into a V-shaped trough but doesn't stop at filling the trough to the top. The company continues to add molten glass until the glass begins to overflow the sides of the trough. Automated robotic arms draw the sheets of glass from the edge of the trough. Each sheet is just over half a millimeter thick.
If you were to use this glass for a screen on your electronic devices, you'd end up with a very clear covering. But it's not damage-resistant like Gorilla Glass -- it's just aluminosilicate glass. To give Gorilla Glass its ability to withstand scratches and cracks, Corning gives these sheets of glass a little bath. Then comes the ion exchange process and after that we get a finished product.
How does Gorilla Glass get into products?
Corning partners with manufacturers and provides Gorilla Glass as part of the product's manufacturing process. The average consumer can't go out and buy a sheet of Gorilla Glass to fit on top of an existing device. In that sense, Corning is an original equipment manufacturer (OEM). The finished product will contain Corning's glass but the finished product will have another company's brand on it.
Because Corning's fusion draw process creates thin sheets of glass that don't inhibit applications like capacitance touch screens, you may see a lot more smartphones and tablets that include Gorilla Glass in their construction. Corning's manufacturing process and the explosion in popularity of portable devices may be timed just right to propel the company to success. Right now company latest Gorilla Glass can be seen on some of the latest devices in market.
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