Comparing Smartphone Displays

by November 18, 2014 0 comments

The smartphone industry has developed and progressed dramatically since the days when the display in your mobile phone was required only to show the number of the person calling. Gradually more features were added to help you view emails, click and record photos and videos, etc. The display of a smart phone is one of the most important aspect to consider when buying a new device because it’s the part you’ll spend the most time directly interacting with. The smartphone industry rotates around various names to describe the viewing experience on your smartphone screen viz. IPS, LCD, LED, Retina, AMOLED etc. Let’s find out what is meant by each of these terms and how are they different from others.
LCD Display
An LCD panel uses light modulating properties of liquid crystals. Each pixel of an LCD consists of a layer of molecules arranged between two electrodes, and two polarizing filters (parallel and perpendicular). These liquid crystals don’t emit light of their own thus a backlight is required to generate light. A grid of IC is used to control each pixel by applying electric charge to them. Color are created with using red, blue and green subpixels and are then blended by various degrees to produce different combination of colors. LCD panels produce wider color gamut due to blending of primary colors but wider range is not better everytime as it can produce oversaturated images and images can also look distorted at times. AMOLED screens do not have this issue as they have individual pixels that can be turned on/off to produce range of colors. LCD screens produce some of realistic colors but do not offer as wide contrast ratio as AMOLED screens. LCD panels do not produce deep or clear blacks.
TFT-LCD Display
A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display (LCD) that utilizes thin-film transistor (TFT) technology to enhance image qualities such as addressability and contrast. By far this is one of most common type of display used in budget smart phones and also comes in some good tablets and phones. Since a mobile phones have larger display and it has large number of picture elements (pixels). Each pixel acts as a little capacitor with a layer of insulating liquid crystal sandwiched between transparent Indium Tin Oxide Layers. They are created from a thin film of amorphous silicon that is deposited on a glass panel. Transistors take up only a small fraction of the area of each pixel and the rest of the silicon film is etched away to allow light to easily pass through it. The TFT-LCD display has narrow viewing angles and also if you look at them off from the center it can be hard to see what’s on the display. You will also have poor visibility in direct sunlight. Color richness is dull. TFT LCD panels consume less power.
IPS (In-Plane Switching) Display
IPS is a screen technology used for LCD displays and is a marked improvement over TFT-LCD panels. In-plane switching includes organizing and switching the molecules of the liquid crystal (LC) layer between the glass substrates and the movement of these molecules is in parallel instead of perpendicular which in turn decreases the amount of light spread across panel giving IPS displays wider viewing angles and good color reproduction. Thus IPS panel display consistent, more accurate colors from almost all viewing angles. IPS displays are costlier than TFT-LCD and are most common in High-end smart phones. One of the disadvantage of IPS panels is they consume more power.
OLED (Organic Light Emitting Diode) Display
An OLED is a light emitting diode in which emissive electroluminescent layer is composed of thin film organic compound which emits lights in response to an electric current. In OLED technology a layer of organic material (carbon based) is sandwiched between two conducting sheets (an anode and a cathode). When electric pulse is applied the two conducting sheets, electro-luminescent light is produced directly from the organic material sandwiched between. OLED displays can use either passive-matrix (PMOLED) or active-matrix techniques. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes. An OLED display works without a backlight; thus, it can show strong black levels and is thinner and lighter than a liquid crystal display (LCD). In low light conditions such as a dark room, an OLED screen can achieve a higher contrast ratio than an LCD. Since it does not require any light to produce black, OLED’s are better compared to LCD, are brighter and produce vibrant colors and have wider viewing angles. OLEDs also have a faster response time than LCDs.
AMOLED Display
As OLED is a specific type of thin-film-display technology in which organic compounds form the electroluminescent material whereas an active matrix represents the technology behind the addressing of pixels. An AMOLED display consists of an active matrix of OLED pixels in order to produce light (luminescence) upon electrical activation that have been incorporated in a thin-film-transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel. Each pixel is composed of Red, Green and Blue subpixels which turns on and off in combination to create any color combination. The two TFT backplane technologies, namely polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are used today in AMOLEDs. AMOLED displays deliver higher refresh rates and consume less power which makes AMOLED convenient for portable electronics such as smart phones where power consumption is crucial in accordance with battery life. AMOLED screens have brilliant color reproduction, higher brightness levels and good contrast ratio. Also since the light in the display screen comes from individual pixel instead of producing from a backlight thus to create a black color relevant pixels are dimmed off or turned off giving deep black.
Super AMOLED is Samsung’s defintion for an AMOLED display with an integrated digitizer, meaning that the layer that detects touch is incorporated into the screen, rather than on top of it. Super AMOLED uses Samsung’s PenTile matrix Layout. This matrix has fewer subpixels and uses green pixels interleaved with alternating red and blue pixels. Color gamut is high,images are much more granular, clear and sharp in Super AMOLED and color richness is high than LCD panels. Also as the touch sensitivity is integrated into screen itself, the result is not only thinner, lighter screen more touch sensitive but also less reflective making it easy to view in direct sunlight. Since there are fewer subpixels that the battery has to power, Super AMOLED screens have battery saving efficiencies.
Retina Display
Retina Display is a brand term used by Apple for screens that have a pixel density high enough that the human eye is incapable to identify individual pixels at a typical viewing distance. The term is specifically used for several Apple products including iPhones, iPads, MacBooks etc. Retina display screens are good, sharp, colorful and bright. The main difference in Retina and other displays is in fine details and text. The lettering, texts in iBooks or Kindle app are clearly different and the text is much sharper and crisp. Retina displays have wide, sharper viewing angles and colors are much more vivid and vibrant. Apple’s Retina display is hard to beat in terms of pixel density and resolution.
When buying a phone, the screen will always be a factor, but it isn’t going to be the only deciding factor. The ideal option must depend on what you will use your screen for. If you want to watch movies, play games AMOLED will be a better choice giving higher contrast ratio, and rich colors. On the other hand if web surfing, document viewing is more important to you than LCDs and Retina Displays will be more preferable offering crisper texts and making it easier to read on screen for long periods.

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