PC MONITORS

How do monitors work? Well first, lets say that there are color guns in the monitor that can regulate the intensity of a given color. There are normally three guns - RED, BLUE, and GREEN. Combinations of color and intensities of the colors can be mixed to represent any color desired. Some monitors are capable of only 2 colors, others 4, 16, 256, and even some that can represent "true" color (or over 16 million colors). Actually, you have no need for true color since you can't possible distinguish that many colors with your eyes, and it takes a tremendous processing power to calculate and display so many colors.

The color guns project beams of light (color) to various parts in a mix. These beams of light are called beams of electrons. They pass thru the deflection yoke in order to display them at the proper location on the screen. Your video card is responsible for sending the signals to the three color guns.

The beams from the color guns activate phospor dots on your screen. The amount of power in each beam determines the intensity of that color. Remember, a pixel is a single dot on a screen, but the pixel is made up of the three colors. Different amounts of power for each of the three guns determines the color displayed as the three dots mix for the pixel color.

Now, we can review the levels of resolution and the acronyms for them that have been developed over the years.

In the beginning there was very low resolution (300 x 200 pixels), but it has changed over time to reach the high levels of today! This resolution began even before the PC revolution; however, it was the PC revolution and evolution that caused the high resolution displays (monitors) to be made available to the general public at a reasonable (or affordable) cost.

DISPLAY STANDARDS:

  1. CGA - Color Graphics Array (1982) had several versions. The original concept was a 640 x 200 pixel screen, and later evolved to 640 x 400 (double-Scanned CGA) pixel screen resolution. These figures (640 x 200) means that there are 640 columns and 200 rows of pixels on the screen, or about 128,000 pixels on a early CGA screen! That is a lots of little lights to turn on!

    The CGA standard had the ability to display 16 bright colors, assuming you understood that black, dark grey, light grey, and white were "bright" colors at 640 x 200 pixel resolution.

    Later the double-scanned version of CGA had a resolution of 640 x 400 pixels. This allowed for sharper images, but still used the CGA standard. Double-scanned CGA is great for characters; however, it gave no increase in sharpness with graphics.

  2. VGA - Video Graphics Array (1987 by IBM) basically was intended to improve the capabilities of the CGA or EGA standards by going to a 640 x 480 pixel resolution. It was backward compatible with all previously defined video standards.

    In text mode, you use 16 foreground colors and 8 background colors, make characters blink with 8 extra background colors. In text mode, each character was 9 x 16 dot boxes, so at 80 columns x 25 rows, the screen display was 720 x 400 pixels.

  3. SVGA - Super Video Graphics Array. SVGA is a term used by the Video Electronics Standards Association to refer to all modes and resolutions beyond the basic 640 x 480 graphics mode of VGA.

    VESA specifies standards for how your software to determine what the display adapter does. The VESA does not tell a manufacturer how to build a display adapter. It does tell how your programs connect to your display adapter, and how the rules for connecting your monitor.

    These VESA standards include standards at resolution levels of

    1. 800 x 600
    2. 1024 x 768
    3. 1280 x 1024
    4. 1600 x 1200

A term called "dot-pitch" will also be very important to you. The "dot pitch" is a term used to specify the distance (in millemeters) between dots of the same color on the screen. Dot Pitch is used with something called a "shadow mask". This is a thin film of metal which has tightly spaced holes in it. It determines how the color dots in a pixel are aligned. The lower the number for dot-pitch, the better resolution you will have. A "shadow mask" works something like this:

  1. The shadow mask is located inside the display tube, a short distance behing the phosphor coating of the screen.
  2. The mask and the phospor coating are arranged so that the electron beam can only hit the phospor dots of one color.
  3. The other two colors of the BGR group are in the "shadow" of the mask, and cannot be seen by the beam.
  4. The phosphor dots must be spaced at the same distance as the holes in the mask.
  5. The hole spacing of the mask determines the "dot-pitch" of the CRT.
  6. The lower the dot-pitch number the better the resolution. The dot-pitch number specifies the spacing between the dots. So, the lower the number, the closer the holes, and the more dots that cam be concentrated on a particular of the screen; consequently, the higher (better) the resolution or picture quality.

Remember, the smaller the dot pitch number, the better the quality!

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