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More On Monitors
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There are two popular types of monitors. Until a few years ago, most everyone used a CRT (Cathode Ray Tube) monitor. The CRT uses a large heavy glass vacuum tube to produce the images. It fires 3 electron beams at a phosphorous coated screen. When the electrons hit the screen, they emit light. As a downside, these monitors are large, heavy and relatively inefficient. They do have some good points though. They can be viewed from an angle with little or no change in the image and they are inexpensive. Many people are now buying LCD monitors to replace aging/failing CRT monitors. The LCD monitors are much smaller overall and typically have a much sharper image than a CRT monitor. They are typically only a few inches deep so they take up much less space on the desktop. Although they're more expensive than CRT monitors of comparative screen size, the prices are coming down quickly. Above I mentioned that a CRT monitor uses electron beams to generate light to produce an image. In an LCD monitor, there is a backlight that produces the light. The LCD panel simply allows light through or blocks the light. In the images below, you will see an LCD monitor at various distances and magnification. At the highest magnification, you can clearly see the individual cells that make up each pixel. The following image is a partial screen-cap (capture) of a blank Internet Explorer page. As you can see, only a tiny section of it is displayed. It's approximately four times the normal size. Each of the letters look as if they're made of little blocks. That's because they are. Each block is a pixel (Picture Element). These pixels make up everything we see on the screen. There are thousands (or more) of them on a typical monitor. On a common 17" LCD monitor with a 'native' resolution of 1280x1024, there are more than 1.3 million pixels (1280 make up each horizontal line and there are 1024 horizontal lines).
![]() In this picture of a real monitor you can see the vertical columns of pixels but it's difficult to see the horizontal rows of pixels.
![]() In the next image, you can start to see the rows of pixels and you can see that the screen is truly made up of little blocks.
![]() Here, you can start to see something a little more interesting. Each pixel is composed of the three primary colors of the 'additive' color scheme (red, green and blue). When these three colors are produced at the same levels, you get white (or gray when less than 100% of the light is allowed to pass). A monitor with a native resolution of 1024 by 768 has 1,024 RGB elements from left to right and 768 from top to bottom.
![]() This is as tight of an image as I could get. You can clearly see the three output colors. In an LCD monitor, the three color filters allow only their respective colors through from the bright white backlight. When they all allow the maximum light through, you get white. If all allow only 50% through, you get gray. By changing the level of the individual color elements in each pixel, you can get virtually any color.
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Perry Babin 2005 All Rights Reserved
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