Computer Monitors



Slowly but surely the old-fashioned CRT (cathode ray tube) monitor is becoming a thing of the past...

It was only about 5 years ago that a 21” CRT cost close to $2,000 while a 17” cost just under $1,000 and a 15” was about $400. Now you find 17” monitors packed with $500 complete systems! You can buy a 19” for just over $100.

LCD or flat panel monitors just a few years back were $500 or more. Today you can buy them for $200 or less in a 17” size and get a 19” for about $400. These screens use less power, take up little room, are extremely light and throw off next to no heat.

No matter which monitor you buy they all have some common elements that mean a lot based on the type of usage you intend for your work.

The first is size of pixels and “pitch” which is how large the dots are, how much black separates them and how readily you can see this “matrix” at close range.

Older CRT monitors went from a low of .24 to a high of .31. The lower the number the less you saw the black area and “dots” or “squares” that make up the picture. The .31 dot pitch looked like you put a window screen over the face of the monitor. Well, maybe that’s an exaggeration, but it does paint a good picture in your mind! The .24 pitch monitors didn’t show the dots even up close. Remember, a computer monitor is not like a TV set. You sit a foot or two away from the monitor screen, not half-way across a room!

Price wise back in the 1990’s the .24 dot monitors were $500 while the .31 dot monitors were $200. You found the latter on system from Radio Shack for $1,100.

Scanning rate in both horizontal and vertical is the next factor. The faster the scanning rate the less the flicker on the screen and if you stand back 20 or so feet from almost any monitor you can start to see the flicker.

What is the scanning rate and why is it important? This is how the image is drawn on the screen and how fast (or often) it is refreshed. If the image is drawn just once it would be like a camera flash used to take pictures inside. A quick burst of light and then slowly your eyes get used to the dark again. You’d see a faint after image for something less than a second. So, they re-paint the screen at a rate in two directions. This is fixed for a home TV set and based on the wall socket current of 60 times a second in the U.S. and 50 times a second in Europe. For a monitor is varies with the resolution of viewing and it is controlled by a circuit that generates the picture image in cycles that vary from 35 a second to 95 a second. The slower the refresh rate the more flicker you see and in some low cost monitors you can even see the darkening scan lines at resolutions such as 1280 x 1024. Some monitors can’t handle resolutions above 800 x 600 with full color at all! That’s why some monitors cost less than $100. The best monitors have “multi-sync” capabilities than can match your card sync rate for both horizontal and vertical. Those monitors with “fixed” sync will only work with some video cards and only at some resolution rates. Trying to use these cards at other rates results in multiple or blurred images.

Resolution is another factor and this depends on both the color card that is installed (or comes with your integrated computer system) as well as the monitor. The resolution matrix and scanning rates between the monitor and card must match closely to get above 800 x 600 with true color (24 or 32 bit). The best monitors provide 1600 x 1280 at 24 bits (true color) while most monitors easily handle 1280 x 1024 at 24 bits (true color).

Color depth is a factor that depends on resolution and card. Today most monitors provide from 24 bit true color, but a few still only offer 16 bit color at higher resolutions.

Additionally, in the case of LCD screens lag time, brightness and contrast are also important factors.

Lag time is how long it takes the LCD screen to react to something, such as a mouse move and it’s rated in ms (milliseconds) of which the smaller the number the faster the reaction time (in other words a 43 ms lag time is better than a 100 ms lag time).

Contrast is in a ration of dark to light expressed as 400:1 or 500:1. Once again, the larger the number the more shades of “gray” or pastel between one extreme and the other. So a 600:1 is generally better than a 400:1.

Brightness can also be important and you again want something with a higher number. One rated at 300 is better than one rated at 250.

As an example:

We looked at the following 17” LCD brands all priced in the $200 - $300 range:

Specification SVA DELL SAMSUNG

Contrast` 400:1 450:1 600:1
Brightness 250 250 300
Response Time 45ms 25ms 12ms
Vertical Freq 75khz 76khz Varies
Horizontal 80khz 80khz Varies
Dot Pitch .264 .264 .264
Resolution 1280 1280 1280
Color 16.7m N/G 16.2m


The clear winner in most catagories is the Samsung with comparable color, more contrast, brightness, faster response time plus variable frequencies for vertical and horizontal so it will match more cards and systems.

 





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