CRT, LED and LCD Computer Monitors

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We use computer monitors on a daily basis spending much time in front of them but on the other hand it is really fascinating that we basically know just a little about them. Most people do not know how they work; many also do not know which types of computer display screens are available on the market. On following page here on my site, I will do my best to explain and reveal most important things and factors related to computer monitor just like aspect ratio, refresh rate, resolution, dot pitch, also I will write about LED, LCD, OLED and CRT monitors and many more related things. Spend few minutes and you will find out much!

First computer monitors, as you probably know, user cathode ray tube for image reproduction and we call those types of monitors CRT. New devices available on the market use thin film of transistors called TFT. Those are used in LCD monitors and also in LEDs (I will explain similarities and dissimilarities of LCDs and LEDs later in article). As every computer needs to have monitor, it is most used output device. Its job is to reproduce data from computer and display it in form of text and graphic.

Many times when people are speaking about monitors they say “flat screen” or “flat panel” but in many cases they really do not understand what the difference between them is. Easiest way to separate flat screens from flat panel is to take a look at next image.

So, now when we know and understand that we have two major types of computer monitors: CRT and LCD, and when we understand what are flat screen display screens are in fact CRT while flat panel displays are LCDs and LEDs, we may proceed. First of all, let’s say something about CRT displays.

Flat Screen CRT computer monitors
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Very first computer monitors used cathode ray tubes (from that we have term CRT) for image and graphic reproduction. Earliest models in 1980s were video display terminals and monitors were physically attached to the keyboard and computer. They were monochrome and because of that image quality was very poor. With advancements of computer technology and IBMs invention of color graphic adapter and enhanced graphic adapter later in 1984 computer monitors were producing 16 colors. Through 1980s and 1990s CRT monitors and technology was dominant on the PC market mainly because of cheap production cost. (Source: WikiPedia - CRT Technology)

From the beginning of year 2000, demand for CRT monitors have dropped significantly mainly because of lower price of LCD monitors. CRT is officially dead technology as brand name manufacturers do not produce those anymore.

Flat Panel LCD computer monitors
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Using and Implementing of liquid crystals began in 1990s. Increasing usage of LCD begun with TFT variation of liquid crystals that is nowadays also dominant technology that is used for manufacturing of LCD display screens. During that time only laptops had this type of display screens as, first of all, laptops were extremely expensive during that time and they needed to be thin as possible and to use small amount of energy.

Of course, first LCD displays were very expensive but during time price declined. They become more and more popular as they are much lighter compared to CRT displays, use much less power and they are not that bulky and use considerably less space on the desk. Additionally, thanks to much less flickering, LCDs are much better than CRT as they reduce eye strain. More about advantages and disadvantages on WikiPedia Advantages and disadvantages of LCD page.

During past few years, on the market we may find LED display screens also. Many people do not understand how LED monitors work and what they are. This is often seen on the forum boards where people tend to favor LCD or LED. First of all, you need to understand that basically LED monitors are in fact LCD monitors using different backlight for illuminating LCD cell. They are not truly LED displays, but people and manufacturers tend to call them “LED TV”. More about LED display screens on my other website: LED Monitors

Flat Panel LED computer monitors
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Since I have already dedicated one whole website to the LED backlight display screens and you may find it following previous link I will not bother you much here about whole technology. Here I will give you just few explanations what they are and how they work.

So, as I have previously mentioned, LED backlight displays are just the same as LCDs since whole technology behind both of them is same, main difference is in backlight that is used for illuminating LCD cell. LEDs for illumination use white diodes that are in computer monitors placed around the monitor rim and we call those Edge LED monitors. Of course, there are also RGB LEDs (red, green and blue diodes are placed behind the panel) and Full Array LEDs (diodes are placed behind the screen).

When comparing Edge LED (that are most common in computer monitor production) and LCD displays, we may say that their performances are pretty much similar, although LEDs according to manufacturers have longer lifespan. Also, LEDs appear to be brighter, thinner and less weight. When talking about picture quality that pretty much differ from one model to another but we could say that LEDs in overall can produce a bit sharper and more vivid colors.

OLED computer monitors
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In organic light emitting diode (OLED) electroluminescent layer is thin film of organic compounds that is capable of light emitting when electric current is applied. Layer of organic semiconductor is placed between two electrodes and at least one is transparent. They are mostly used as TV screens, computer monitors, in mobile phones and PDA devices. OLED displays do not need backlight and because of that they are able to produce much deeper black levels and can be much thinner than LED and LCD monitors. Since OLED technology is pretty new, they are extremely expensive at the moment and 25 inch OLED computer monitor can cost you around $6000 at the moment but we expect that price will drop in near future. More about OLED displays you may read on WikiPedia -OLED,


Computer Monitor Factors and Performance Measurements
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Luminance – is photometric measure and represents luminous intensity per unit. It basically describes how much light is passed through or is emitted from particular area. It is measured in candela per square meter (cd/m2) and indicates how bright is the surface so in computer monitor industry it represents the brightness of the display screen and it vary from 50 to 300 candelas per square meter.

Aspect Ratio – represent ratio of horizontal to the vertical length of the image. In most cases have aspect ratio of 4:3 which is common video graphic aspect ratio, while widescreen monitors have image display aspect ratio of 16:9 that is universal ratio for high definition television. Cinema aspect ratio is 21:9 (or 2.33:1) that at the moment use just Philips and Vizio through 2560x1080 (2.37) and for now it is not yet standardized.

Viewable image size – is generally measured diagonally and represents surface area of the computer monitor that displays image. CRT monitors have viewable size about 1 inch smaller than the tube while in LCD and LED monitors it is measured from corner to corner and represent whole viewable area. Because of the different type of measuring of CRT and LCD displays, 17 inch LCD (LED) is equivalent for 19 inch CRT monitor.

Display resolution – during 2002 common display resolution was 1024x768 and most of the internet sites and multimedia were redesigned from 800x600 to new, higher format. Many computer applications and video games use higher resolutions like UXGA (1600x1200), SXGA+ (1400x1050), WXGA (1280x720), WSXGA+ (1680x1050) and other. In 2010 multiple manufacturers started producing monitors with 2560x1440 resolution and from May 2011 maximum resolution for computer monitors is 4096x2160.

Dot Pitch – is computer monitor specification that describes distance between sub pixels of the same color in millimeters. The smaller dot pitch distance is (larger number) the better as picture will appear sharper. It is also measured in dots per inch.

Refresh Rate – present number of times in a second that display is illuminated (draw data) and it is limited by monitor response time. 16 inch CRT monitors had refresh rate of 60-72Hz, larger monitors had 72Hz refresh rate or higher. It is a little bit different with LCD monitors and closes equivalent is frame rate which is in LCD soften locked at 60fps (frames per second).

Response Time – presents needed time that monitor takes to go from black to white and back to black again. It is measured in milliseconds and lower number means that monitor response is faster and therefore is better. Typical black-white-black response of LCD monitors is from 8 ms to 16 ms and 2 to 6ms for gray to gray transition.

Contrast Ratio – is defined as the ratio of luminance that display screen is capable of producing ranging from brightest white to darkest black. When purchasing it is better to purchase display with higher contrast ratio but since this measure is not standardized manufacturers tend to put fake numbers stating dynamic contrast ratio measures.

LED and LCD computer monitor reviews
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Viewsonic VX2450WM-LED 24-Inch (23.6-Inch Vis) Widescreen LED Monitor with Full HD 1080p and Speakers - Black
In case that you are browsing around trying to find good and cheap LED monitor, my personal recommendation is this particular ViewSonic VX2450WM-LED. It is 24 inches widescreen LED monitor with 1920x1080 pix resolution and Full HD support. First of all, compared with similar LCD monitors, this one uses 50% less energy – 28-30W so it will save huge on your electrical bill. With price less than $200 I could say that it is really best buy on the market today! ViewSonic VX2450 has 20.000.000:1 dynamic contrast ratio.

Advantages: According to user reviews, it produces amazing bright and vivid image quality. It has just right matte finish; glare that can occur is reduced while there is no sacrifice of brightness or image sharpness.
Disadvantages: Monitor wiggles while touch controls are used because it is very light. For some persons the screen could be very bright so it is advisable to lower brightness to proper level. It is not great for graphic designers as colors shift somewhat with changing of viewing angle.
More about Viewsonic VX2450 on its page here: ViewSonic VX2450

HP 2511x 25-Inch LED Monitor - Black
This is one very interesting LED monitor from HP. It is 25 inch widescreen with Full HD 1920x1080 pix resolution and 3.000.000:1 dynamic contrast. The base of this HP display screen is adjustable and it can tilt. Control buttons have nice tactile and they are very functional. You are able to choose from four predefined presets: text, photos, movies and gaming. Image quality is outstanding, black text on white background is very readable, clear and sharp. It is able to produce very deep dark black with slight color bleed on the bottom edge of the screen. Photo quality is also very good but you may notice some color degradation when you move your head around. Playing games using HP 2511x 25-Inch LED Monitor is pretty nice since colors are very bright and clear and 5ms response time provides additional satisfaction as there is no ghosting effect during fast moving scenes and effects. In overall, for this price you will get more than you pay as it is pretty amazing LED monitor good for watching movies, playing games and every day work on your computer.
More about HP 2511x 25 inch LED monitor you may find here: HP 2511x 25-Inch LED Monitor - Black

Acer ET.CV3WP.E05 19-Inch Widescreen LCD Monitor (Black)
In case that you really have tight budget and if you want to purchase LCD monitor one of the best bargains is Acer ET.CV3WP.E05 19-Inch Widescreen LCD Monitor for sure. With price that is around $90 you will not get much better than this computer monitor. It is 19 inch widescreen with 1440x900 resolution, 250cd/m2 brightness, 50.000:1 dynamic contrast ratio and 5ms response time. This particular computer monitor is pretty descent with fine image quality and good brightness. Image quality is really solid and without a problem you may use it in any environment, office or at home. Of course, for less than $100 you can not expect performance like on mainstream models that cost few times more, but I believe that you will be satisfied with what you get from it. If you don’t have high expectation and you want to use your monitor to perform everyday work it Acer ET.CV3WP.E05 will do everything just ok without a problem.
More about this Acer monitor you may find here: Acer ET.CV3WP.E05 19-Inch Widescreen LCD Monitor

Samsung B2430H 24-Inch Widescreen LCD Monitor - Glossy Black
On the other hand, if you really want LCD computer monitor and if you are prepared to spend $200 to purchase truly great monitor, than Samsung B2430H 24-Inch Widescreen LCD Monitor - Glossy Black is great deal. It is equipped with HDMI connectors, MagicEco function which enables you to work using less brightness in order to reduce energy usage. Moreover, it has 70.000:1 dynamic contrast ratio and 5ms response time with razor sharp image quality both on static images and text. While playing games, you will never notice ghosting effects or motion blur thanks to its amazing response time. When you take a look at it, you will notice that it is by fire more appealing than most models. Color and image quality is on Samsung level, so no problem can be found. Only disadvantage listed by consumers could relate to its hidden touch buttons and software that comes with it. Advice is to not install provided software on Windows 7 that comes with it. Everything else when talking about Samsung B2430H 24-Inch Widescreen LCD Compute Monitor is on highest possible level.
More about this monitor you may find here: Samsung B2430H 24-Inch Widescreen LCD Monitor - Glossy Black

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