Liquid crystal display more commonly known by its short form the "LCD" has taken the world by storm. LCDs are nowadays used in almost every aspect of life as a form of display. LCDs came about to replace the older CRT(Cathode ray tube) monitors. The older CRT monitors were plagued by large size and large power consumption. LCDs was created initially to overcome this handicap. As time progressed it came about to completely replace the CRT as a viable display option. LCDs hosts a number of advantages compared to the CRTs. They have capability to achieve larger screen size, an almost miniscule power consumption compared to the CRT, thinner panels and an almost equal colour production coupled with super fast response times. They are also cheaper to produce and easier to maintain.
However the LCD still remains an enigma to the vast majority. They find its working very hard to understand and its specifications too cumbersome to fathom. Thus they give up and surrender the choice of buying an LCD into the hands of others, blindly obeying what they say. Even to those who understand they get confused between the various features of an LCD.
How LCD's Work
This is where it gets quite technical. so get your reading glasses up and concentrate
The basic LCD consists of the following layers
An LCD uses something called liquid crystals which form the core of any LCD panel. The term liquid crystal may be quite difficult to understand. Imagine something in terms of jelly. Something semi-solid yet transparent. These crystals exist in a state between liquid and solid. They are very easily influenced by temperature and pressure changes.(that's why LCDs act crazy when exposed to Delhi heat)
Basically these crystals consist of layers of molecules lined at a certain angle to each other like at specific angles(smectic type) or more specifically a slow turning helix (chiral smectic type)
Today's LCD panels use electric currents to align the angles of different layers to their preference. Imagine this to be like a gateway wherein each layer slowly changes the angle of the light going through so that it finally reaches its desired angle(see image below).So the Liquid crystal layer acts only to filter the rays and not produce it!! this is an important aspect to remember as this helps in understanding illumination.
The crystal layer helps polarized(basically light with only one direction of spread) light reach the other end at a different angle thus controlling it. Pixels as such are a single column or row layers of such liquid crystal molecules....
Image courtesy of Howstuffworks
Passive and active matrix
Passive matrix is the original prototype of the LCD mechanisms. it uses circuits to control the colours displayed by each pixel by regulating current flow in rows and columns. It sounds simple but is plagued by slow response times and blurry margins due to spread of current as several rows are controlled by one circuit. Outdated
Active Matrix uses transistors in the form of Thin Film transistors(TFT) to control this pixel excitation and colour formation wherein each row and columns has an individual transistor or capacitor, so the problem of spread is minimized. Shades and colours are produced by slight modification of voltages. Most commonly used now.
Illumination
The Liquid crystal layer basically as explained above is only a gateway and does not illuminate on its own.. then where does light come from may be the question.. Two types of sources are generally utilized
1. Cold cathode fluorescent Lamps or CCFL - The majority of LCDs out there still use this technology. Similar to neon lamps (like a tubelight). Produce good output but lighter shades of blue. Second best colour gamut upto 97%
2. LED Backlit-
a. White edge LED(W-LED)- the LEDs are placed at the edge of the screen and diffuse light inwards. Their use is now starting in consumer LCDs mainly laptops and smaller versions such as your dear iPhone. Cheaper than RGB but colour gamut worst of the three upto 68%. Edge lit unit in the pic below indicates the W-LED placement.
b. RGB LED - contain these LEDs behind the panel as a triad. superior to white LED. Best colour gamut but the most expensive of the three. Offers upto 114% NTSC colour gamut. The direct-lit unit in the picture below shows the placement of RGB LEDs. Colour Gamut refers to the range of colours the Backlight can output. 100% approximately equals 16.7 million colours.
Types of LCD panels
Basically three main types exist
1. Twisted nematic or TN panels- The most basic type and the grand old daddy of LCD panels. It follows the principles stated above to the dot. They are generally deficient in displaying black, to a certain extent which the recent models have improved vastly upon. But these panels have the fastest response times. Hence Gamers are advised to use such panels. However they have poor viewing angles limited to max 170 degrees. upto 1080p only.
2. Vertical alignment or VA panels- They are superior to TN panels in colour reproduction and better viewing angles but response times are poorer than TN panels. Their variants are used in television sets today. Different advancements include MVA (mutli-domain vertical alignment) and PVA (pattern vertical alignment).
3. In-Plane switching or IPS panels- The great IPS panels, part of the Dell U2311H so vociferously recommended on TE. The most recent of the panels. exceptional colour reproduction and large viewing angles upto 180 degrees but slowest response times of the three. This has been rectified upto a certain extent in the newer IPS models but response times still remain slower than TN panels. It uses two transistors instead of the traditional one transistor as in others. This reduces the backlight bleed or spread and thus we get far superior colour. Various varieties exist Horizontal IPS (H-IPS), Enhanced S-IPS (sometimes called E-IPS), Advanced Super IPS (AS-IPS), and "Economy" IPS (called e-IPS) panels can offer responsiveness to rival both. Used mostly by developers..
Other varieties are just offshoots of these. Modern day LCDs use response time compensation to improve response times.
LCD specifications
This is the most important chapter for buying an LCD.. so pay attention once again
1. Size: The size of any LCD is measured by using the diagonal. Various sizes exist starting from 15 inches to 54 inches and more.
2. Aspect Ratio: Ratio of height vs breadth. Mainly are 4:3, 16:9 and 16:10. 16:10 has now been almost phased out, but of the three it is the best and 16:9>4:3. So if u get a 16:10 grab it for Crysis will be unbelievable on it.
3. Resolution: It indicates no of pixels in each dimension. Each monitor has a native resolution, anything above or below this the monitor stretches to fit across its panel and may thus appear skewed. So keep a monitor at its native for best viewing.
4. Brightness and Contrast ratio: Difference between darkest black and whitest white is contrast and brightness you all know .. always look for static contrast as dynamic contrast is an arbitrary measurement. many default at 1000:1
5. Viewing angle: As explained previously in the types of panels viewing angles vary with types of panels. Given as horizontal and vertical angles. The TN panel generally maxes out at 170 degrees and the IPS may reach upto 178. Choose a panel with maximum angle so as to facilitate good viewing or else you have to be stuck smack in front of the screen to do anything
6. Refresh rate: It is defined as frequency at which the monitor refreshes itself. Most modern day monitors use 60 or 75Hz refresh rate. Upto 120hz have been released recently. That is the monitor refreshes itself so many number of times in minute. Any hardware like a graphics card providing rates greater than this refresh rate will cause out of sync error on the monitor.
7. Response Time: Time taken for a pixel to change from one colour to the other. Faster is better for Gamers especially..
8. Pixel pitch: Distance between individual pixels.. You might have guessed it but the closer the better.. as a matter of fact the lesser the screen size the lesser the pixel pitch. For ex: Dell u2211h has lesser pixel pitch than a u2311h so more colour clarity with the u2211h.
That concludes this article. I have overlooked certain minor and intricate aspects as in the greater scheme of things these hardly make any difference to normal consumers. So hope this helps you next time you browse for an LCD.
However the LCD still remains an enigma to the vast majority. They find its working very hard to understand and its specifications too cumbersome to fathom. Thus they give up and surrender the choice of buying an LCD into the hands of others, blindly obeying what they say. Even to those who understand they get confused between the various features of an LCD.
How LCD's Work
This is where it gets quite technical. so get your reading glasses up and concentrate
The basic LCD consists of the following layers
An LCD uses something called liquid crystals which form the core of any LCD panel. The term liquid crystal may be quite difficult to understand. Imagine something in terms of jelly. Something semi-solid yet transparent. These crystals exist in a state between liquid and solid. They are very easily influenced by temperature and pressure changes.(that's why LCDs act crazy when exposed to Delhi heat)
Basically these crystals consist of layers of molecules lined at a certain angle to each other like at specific angles(smectic type) or more specifically a slow turning helix (chiral smectic type)
Today's LCD panels use electric currents to align the angles of different layers to their preference. Imagine this to be like a gateway wherein each layer slowly changes the angle of the light going through so that it finally reaches its desired angle(see image below).So the Liquid crystal layer acts only to filter the rays and not produce it!! this is an important aspect to remember as this helps in understanding illumination.
The crystal layer helps polarized(basically light with only one direction of spread) light reach the other end at a different angle thus controlling it. Pixels as such are a single column or row layers of such liquid crystal molecules....
Image courtesy of Howstuffworks
Passive and active matrix
Passive matrix is the original prototype of the LCD mechanisms. it uses circuits to control the colours displayed by each pixel by regulating current flow in rows and columns. It sounds simple but is plagued by slow response times and blurry margins due to spread of current as several rows are controlled by one circuit. Outdated
Active Matrix uses transistors in the form of Thin Film transistors(TFT) to control this pixel excitation and colour formation wherein each row and columns has an individual transistor or capacitor, so the problem of spread is minimized. Shades and colours are produced by slight modification of voltages. Most commonly used now.
Illumination
The Liquid crystal layer basically as explained above is only a gateway and does not illuminate on its own.. then where does light come from may be the question.. Two types of sources are generally utilized
1. Cold cathode fluorescent Lamps or CCFL - The majority of LCDs out there still use this technology. Similar to neon lamps (like a tubelight). Produce good output but lighter shades of blue. Second best colour gamut upto 97%
2. LED Backlit-
a. White edge LED(W-LED)- the LEDs are placed at the edge of the screen and diffuse light inwards. Their use is now starting in consumer LCDs mainly laptops and smaller versions such as your dear iPhone. Cheaper than RGB but colour gamut worst of the three upto 68%. Edge lit unit in the pic below indicates the W-LED placement.
b. RGB LED - contain these LEDs behind the panel as a triad. superior to white LED. Best colour gamut but the most expensive of the three. Offers upto 114% NTSC colour gamut. The direct-lit unit in the picture below shows the placement of RGB LEDs. Colour Gamut refers to the range of colours the Backlight can output. 100% approximately equals 16.7 million colours.
Types of LCD panels
Basically three main types exist
1. Twisted nematic or TN panels- The most basic type and the grand old daddy of LCD panels. It follows the principles stated above to the dot. They are generally deficient in displaying black, to a certain extent which the recent models have improved vastly upon. But these panels have the fastest response times. Hence Gamers are advised to use such panels. However they have poor viewing angles limited to max 170 degrees. upto 1080p only.
2. Vertical alignment or VA panels- They are superior to TN panels in colour reproduction and better viewing angles but response times are poorer than TN panels. Their variants are used in television sets today. Different advancements include MVA (mutli-domain vertical alignment) and PVA (pattern vertical alignment).
3. In-Plane switching or IPS panels- The great IPS panels, part of the Dell U2311H so vociferously recommended on TE. The most recent of the panels. exceptional colour reproduction and large viewing angles upto 180 degrees but slowest response times of the three. This has been rectified upto a certain extent in the newer IPS models but response times still remain slower than TN panels. It uses two transistors instead of the traditional one transistor as in others. This reduces the backlight bleed or spread and thus we get far superior colour. Various varieties exist Horizontal IPS (H-IPS), Enhanced S-IPS (sometimes called E-IPS), Advanced Super IPS (AS-IPS), and "Economy" IPS (called e-IPS) panels can offer responsiveness to rival both. Used mostly by developers..
Other varieties are just offshoots of these. Modern day LCDs use response time compensation to improve response times.
LCD specifications
This is the most important chapter for buying an LCD.. so pay attention once again
1. Size: The size of any LCD is measured by using the diagonal. Various sizes exist starting from 15 inches to 54 inches and more.
2. Aspect Ratio: Ratio of height vs breadth. Mainly are 4:3, 16:9 and 16:10. 16:10 has now been almost phased out, but of the three it is the best and 16:9>4:3. So if u get a 16:10 grab it for Crysis will be unbelievable on it.
3. Resolution: It indicates no of pixels in each dimension. Each monitor has a native resolution, anything above or below this the monitor stretches to fit across its panel and may thus appear skewed. So keep a monitor at its native for best viewing.
4. Brightness and Contrast ratio: Difference between darkest black and whitest white is contrast and brightness you all know .. always look for static contrast as dynamic contrast is an arbitrary measurement. many default at 1000:1
5. Viewing angle: As explained previously in the types of panels viewing angles vary with types of panels. Given as horizontal and vertical angles. The TN panel generally maxes out at 170 degrees and the IPS may reach upto 178. Choose a panel with maximum angle so as to facilitate good viewing or else you have to be stuck smack in front of the screen to do anything
6. Refresh rate: It is defined as frequency at which the monitor refreshes itself. Most modern day monitors use 60 or 75Hz refresh rate. Upto 120hz have been released recently. That is the monitor refreshes itself so many number of times in minute. Any hardware like a graphics card providing rates greater than this refresh rate will cause out of sync error on the monitor.
7. Response Time: Time taken for a pixel to change from one colour to the other. Faster is better for Gamers especially..
8. Pixel pitch: Distance between individual pixels.. You might have guessed it but the closer the better.. as a matter of fact the lesser the screen size the lesser the pixel pitch. For ex: Dell u2211h has lesser pixel pitch than a u2311h so more colour clarity with the u2211h.
That concludes this article. I have overlooked certain minor and intricate aspects as in the greater scheme of things these hardly make any difference to normal consumers. So hope this helps you next time you browse for an LCD.
