Comparing LCD Monitors and CRT Monitors.

Unit 2: Hardware and Software

Topic: Monitor Comparisons

Comparing LCD Monitors and CRT Monitors

Over the past few years, LCD monitors have made significant advances in the market to emerge as a strong competitor to traditional Cathode Ray Tube (CRT) monitors. Now, large monitor manufacturers like Sony are even planning to phase out CRT manufacturing and concentrate on widening their LCD offerings. So, has LCD won the competitive battle? Perhaps not yet, as CRT monitors still hold a few key advantages. Below I will summarize some of the differences of LCD monitors versus CRT monitors, and which holds the current advantage:

Image Brightness: LCD Monitors easily win in this area, offering brightness approximately twice that as CRT monitors on average. This is particularly important for viewing in daytime, high light areas, like a room with many windows. LCD monitors will easily appear brighter than CRT monitors in these conditions.

Contrast: LCD monitors have made great strides to narrow the gap on contrast. Contrast is important for viewing in low light situations and ensuring that black tones appear black (rather than muddy greys), and is most important for gaming and movie playback. Although CRT monitors pull of the victory, the margin of difference is now minor, with the best LCD monitors matching CRT monitors for most practical purposes.

Colour: CRT monitors still hold the advantage in regards to colour purity and quality. LCD monitors have again made great improvements here, and now offer bold, brilliant colours in many cases. The best LCD monitors are very good, and the average user would be hard pressed to note the difference for basic computing use. For gaming or movie watching, as well as professional-level image editing, this difference can range from slightly to significantly noticeable, especially in a side-by-side comparison.

Size/Weight: An obvious advantage for LCD monitors, and one of their main selling points. LCD monitors can weigh as little as 8 pounds for the smaller screen sizes, and are often just 6-8 inches deep, including the depth of the base stand. CRT monitors by comparison can easily weight 40-50 pounds, are often over 15-inches deep, and are very inconvenient for moving. It goes without saying that LCD monitors help free up a tremendous amount of desk space.

Screen Burn-in: LCD monitors do not suffer from screen burn-in. Although most CRT displays today also avoid this issue, because of the ...

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Screen Burn-in: LCD monitors do not suffer from screen burn-in. Although most CRT displays today also avoid this issue, because of the way LCD monitors are manufactured, there is no risk of burn-in caused by non-moving images that are displayed for a long period of time.

Viewing Angle: CRT monitors do hold the advantage versus LCD monitors here as well. However, it should be noted that LCD monitors have dramatically improved, and current models offer a very wide viewing angle, easily over 160 degrees, which is all that is needed in practical situations.

Response Time: Response time refers to the time the screen takes to update pixel colours. This is very important for gaming and other fast moving images like movie playback. A slow response time will leave a 'trailing effect' where certain pixels seem to lag behind the action. The very best LCD monitors now offer sub 20 millisecond response times, which makes them generally acceptable for gaming. CRTs of course still hold the advantage, since their response time is not noticeable.

Screen Flickering: For those that spend a lot of time on a computer, one of the biggest issues leading to sore eyes and headaches is the screen flicker caused by CRT displays. Although screen flicker is generally not a problem for CRT displays that offer a 85 MHz screen refresh rate, many monitors do not, and default Windows settings are often lower as well. LCD monitors clearly are the better choice here, as there is no flicker at all as a result of the differences in technology.

Magnetic Interference: LCD monitors have the advantage here, and are not affected by magnetic sources, namely speakers. As a result, some LCD monitors even offer integrated speakers, and do not require special shielding. CRT monitors are affected by the magnets in speakers, and depending on the model and closeness of the speaker, can result in a distorted picture.

Power Consumption: Again, LCD vs. CRT, LCD comes out ahead. LCD monitors consume considerably less power than CRTs. Most LCD monitors consume between 20-50 watts of power, while CRT monitors generally consume 50 to over 160 watts.

Dead Pixels: One disadvantage of LCD monitors is that they do include the potential of having so-called dead pixels, i.e. pixels that simply do not function. These pixels cannot be repaired, and can be quite annoying if they are in the main viewing area of the monitor, and are especially noticeable in word processing and other applications where the screen background is generally white. CRT displays do not suffer from this issue, but LCD manufacturing has improved to greatly reduce the frequency of this problem. However, take care to note the warranty for any monitor you plan to buy, and what their policy is for replacing monitors that contain dead pixels.

How LCD Monitors Work

LCD, or Liquid Crystal Display, technology has advanced rapidly since it's commercial inception over a decade ago for use in laptop computers. Technical achievement has resulted in brighter displays, higher resolutions, reduced response times, and cheaper manufacturing processes. It has also allowed manufacturers to greatly increase screen size. Whereas most introductory LCD screens only offer 12 to 14-inches of viewable area, the newest LCD monitors now are available at over 23 inches, with LCD TVs going even further - up to 42-inches. So, how do LCD monitors work?

Liquid crystal displays work by trapping a liquid crystal solution between two panes of polarized glass. The liquid crystals can be manipulated through an applied electric voltage so that light is allowed to pass or is blocked. By carefully controlling where and what wavelength (colour) of light is allowed to pass, the LCD monitor is able to display images. A backlight provides the LCD monitors brightness, and generally has a lifespan of approximately 60,000 to 80,000 hours - about 20 - 25 years of daily 8-hour usage.

Over the years, many enhancements have been made to LCD technology to help improve resolution, image sharpness and response time. One of the latest such advancements is TFT, or thin film transistors. TFT-LCDs make use of a very thin transistor that is applied to the glass during the manufacturing process. The TFT further acts as a switch, allowing control of light at the pixel-level, greatly enhancing resolution and image sharpness. This has been particularly important for improving LCDs ability to display small-sized fonts.

Other advances have allowed LCDs to greatly reduce liquid crystal cell response times. Response time is basically the amount of time it takes for a pixel to 'change colours'. In reality, response time is the amount of time it takes a liquid crystal cell to go from being active to inactive. Response time is described in milliseconds, with the best LCD monitors now coming in at 20 ms and less in response time. Older models often averaged 25-45 ms, leading to a blurring effect when the monitor displayed motion.

Another key advancement for LCD monitors has been the improvement of contrast ratio. This has allowed LCD monitors to greatly improve colour reproduction, and now allows improved gaming and movie viewing. Many manufacturers are now also adding a specially designed low reflective coating that helps reduce glare, increase contrast, allows brilliant colour display.

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