Your guide to the world of TVs

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What is LCD Screen?

A liquid-crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit light directly.

LCDs are available to display a general-purpose computer display or fixed images which can be displayed or hidden, such as preset words, digits, and 7-segment displays as in a digital clock.

Where and When

LCDs are used in a wide range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays, and signages.

What makes a good LCD TV?

Contrast Ratio
A high contrast ratio provides a deeper sense of depth to images being projected on an LCD screen. Therefore, screens with higher contrast ratios are more desirable than LCD screens with low contrast ratios.

Colour
It is common to have an LCD TV that projects oversaturated colours. So for fans of accurate colours, as per how the film or TV show was filmed to look, getting an LCD TV certified with THX mode or a built-in proprietary accurate colour adjustment feature. However, recent LCD TV models have adjustable colour temperature, so the issue of inaccurate colours are lesser.

Brightness
LCD TVs that are dimmer tend to produce better picture quality as compared to brighter ones. Picture quality tends to have more depth and less strain from the viewers’ eyes from prolonged watching.

Pros and Cons

PROS
• Very compact and light
• No geometric distortion
• Can be made in almost any size or shape
• Can be made to large sizes (more than 24 inches) lightly and relatively inexpensively
• Razor sharp image with no bleeding/smearing when operated at native resolution

CONS
• Limited viewing angle, causing color, saturation, contrast and brightness to vary
• Black levels may appear unacceptably bright because individual liquid crystals cannot completely block all light from passing through
• Low refresh rate
• Loss of contrast in high temperature environments
• Poor display in direct sunlight, often completely not viewable

Viewing distance table


What is LED Screen?

A light-emitting diode (LED) is a two-lead semiconductor light source that resembles a basic pn-junction diode, except that an LED also emits light.

Where and When

Light-emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera flashes.

LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology.

LCD vs LED

 Type of TV LCD TV LED TV
Thickness Minimum 1 inch Often less than 1 inch.
Burn-in Not an issue Burn-in is very rare
Life span 50,000 – 100, 000 hours Around 100,000 hours

3D Technology

3D television (3DTV) is television that conveys depth perception to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarised 3D system, and some are autostereoscopic without the need of glasses.

Pros and Cons

PROS
• Carbon emissions
• In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics
• Emit light of an intended colour without using any colour filters as traditional lighting methods need
• Easily be dimmed either by pulse-width modulation or lowering the forward current
• Have a relatively long useful life

CONS
• Must be supplied with the voltage above the threshold and a current below the rating
• The luminous efficacy of LEDs decreases as the electrical current increases above tens of milliamps
• Largely depends on the ambient temperature of the operating environment
• More expensive
• Do not approximate a point source of light giving a spherical light distribution, but rather a lambertian distribution


What is OLED Screen?

OLED (organic light-emitting diode) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound which emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes.

An OLED display works without a backlight. Thus, it can display deep black levels and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions such as a dark room an OLED screen can achieve a higher contrast ratio than an LCD, whether the LCD uses cold cathode fluorescent lamps or LED backlight.

Types of OLED

There are two main families of OLED: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell or LEC, which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. 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.

What makes a good OLED TV?

Brightness
OLEDs are brighter than LCD, or vice versa. Because LCDs use a backlight (of LEDs), their brightness is determined by how bright the backlight is. With OLED, on the other hand, each pixel creates its own light. So there are limits put on the TV as to how bright the entire TV can be.
Black level
Because OLED TVs can turn their pixels off, their black level is nearly perfect. Plasmas can also control their pixels, but are never able to get them to be completely black (always emit some light). LCD TVs can turn off their backlights to create an absolute black, but this is fake, since you wouldn’t be able to see the image.

Contrast ratio
OLED, because it can turn its pixels off, effectively has an infinite contrast ratio. The better local-dimming LCDs can have a decent apparent contrast ratio, though they still don’t look as good as OLED.

3D Technology

3D television (3DTV) is television that conveys depth perception to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarised 3D system, and some are autostereoscopic without the need of glasses.

Pros and Cons

PROS
• Lower cost in the future
• Lightweight and flexible plastic substrates
• Wider viewing angles and improved brightness
• Better power efficiency and thickness
• Faster response time than standard LCD screens

CONS
• Requires process steps that make it extremely expensive
• The limited lifetime of the organic materials
• Colour balance issues
• Water can damage the organic materials of the displays
• Use more than three times as much power to display an image with a white background, such as a document or website


Ultra High Definition TV

What is UHD?

Ultra high definition television (also known as Ultra HD television, UltraHD, UHDTV, or UHD) includes 4K UHD (2160p) and 8K UHD (4320p), which are two digital video formats proposed by NHK Science & Technology Research Laboratories and defined and approved by the International Telecommunication Union (ITU).

A four-step process that includes signal analysis, noise reduction, UHD upscaling and detail enhancement seamlessly convert Full HD programming to 4K resolution so every show is in Ultra High-Def.

With its crystal-clear picture, rich audio and sleek design, the Ultra HD TV offers an immersive and luxurious entertainment experience.

4K resolution is a generic term for display devices or content having horizontal resolution on the order of 4,000 pixels. Several 4K resolutions exist in the fields of digital television and digital cinematography. In the movie projection industry, Digital Cinema Initiatives (DCI) is the dominant 4K standard.

The television industry has adopted ultra-high definition television (UHDTV) as its 4K standard. Using horizontal resolution to characterise the technology marks a switch from the previous generation, high definition television, which categorised media according to vertical resolution (1080i, 720p, 480p, etc.).

Resolution

TV resolutions

3D Technology

3D television (3DTV) is television that conveys depth perception to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarised 3D system, and some are autostereoscopic without the need of glasses.

4K content

There’s no denying that 4K Ultra HD is very much a fledgeling format. Native content is very hard to come by for consumers anywhere.

In more positive news, 4K broadcasts remain on the to do list, with Sony promising to provide technical support to 4K productions, including the 2014 FIFA World Cup. There’s also the outside bet that Sony will enable 4K video on the PlayStation 4 with a firmware update, allowing far more people to access Ultra HD video.

In the meantime there is limited 4K test footage that is for review purposes, along with some content on YouTube and 4K still images. As always, when actually watching native 4K content on a UHD TV the results are spectacular, with a beautifully detailed image and no visible pixel structure.

How far should I sit from a 4K TV for the best picture?

4K Ultra HD is a much more intimate viewing experience than Full HD. In many respects, the best way to view 4K is analogous to the way we view films in a cinema. Old style cinemas were shoe-box shaped and most patrons sat typically 3-5 screen heights away because that was the most comfortable viewing distance.

Contemporary cinemas are wider, and now the optimum viewing distance is 1.5 screen heights back. From this vantage point you can take in all the visual information that’s available and comfortably fill your field of vision. Translated to the home, that makes the most comfortable distance to view a 65-inch 4K screen approx. 1.5m. Of course, in many homes that simply isn’t practical. Consequently, a large 4K screen is probably best viewed at a distance of between 2-3m.

Pros and Cons

PROS
• Allows for 10- or 12-bit depths, which will deliver just over one billion and 68 billion colours
• 4x the detail potential of 1080p HDTVs
• Wider viewing angles and improved brightness
• Better power efficiency and thickness
• Faster response time than standard LCD screens

CONS
• Requires process steps that make it extremely expensive
• The limited lifetime of the organic materials
• Colour balance issues
• Water can damage the organic materials of the displays
• Use more than three times as much power to display an image with a white background, such as a document or website

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