Video Terms and Definitions Chapter Objectives After completing this chapter you will Describe the components of the video subsystem Differentiate among monitor types Understand basic monitor theory and terminology Recommend a resolution for a particular monitor size Describe different types of video memory Be able to install a video adapter and associated software Perform basic video troubleshooting techniques Video Overview Video should be considered a subsystem that consists of the monitor the electronic circuits which send the monitor instructions the connecting cable Video Overview Video Subsystem Video Figure 1 Types of Monitors Different ways of classifying monitors Color or Non color Analog or Digital Type of video adapter used Types of Monitors Monochrome First type to be produced Project a single color white amber or green on black background Text only output no graphics Grayscale Display varying shades of black and white Used by artists and CAD designers Color Display up to millions of colors for text and graphics Types of Monitors Digital Accept digital signals from the video adapter First monochrome and first two types of color monitors Limited number of colors Analog Utilize analog waveforms to generate colors Color variations are limitless Note Video adapter must match the type of monitor Types of Monitors Video Adapters Monitor Types Video Table 1 Monitor Terminology and Theory Monitor size No industry standard but traditionally defined as the diagonal length of the picture tube or CRT Most common sizes are 15 inch 17 inch and 21 inch CRT Cathode Ray Tube Main part of the monitor Commonly referred to as the picture tube Covered by the monitor case which may not allow all of it to be viewed VIS Viewable Image Size Listed by many manufacturers as the viewable area of the CRT to clarify the monitor size Monitor Terminology and Theory Electron gun Directs a beam of electrons at a phosphorous dot on the back of the monitor tube Some monitors have 3 one each for the colors red green and blue Other monitors utilize only 1 to direct the 3 color beams When the beam hits the phosphor the dot glows on the front of the screen All figures icons and letters are made up of these glowing dots Dot triad or dot trio 3 phosphorous dots grouped together at each location on the screen Consists of 1 dot each for red green and blue Electron beam hits the dot s with varying intensity causing the phosphor to glow and create different color intensities Monitor Terminology and Theory Shadow mask A metal plate with holes that keeps the electron beam directed or focused at the proper dot Variations include The Invar shadow mask by Phillips Magnavox reduces heat problem of traditional mask A mask used in NEC s Chromaclear monitors that has elliptical slots instead of holes Pixel short for picture element One dot on the screen created by the convergence of the phosphorous dot trio Smallest displayable unit on the monitor screen Monitor Terminology and Theory Video Theory of Operation Video Figure 2 Monitor Terminology and Theory Picture cell The single image created by 3 different colored phosphorous dots Dot pitch The distance between like colored phosphorous dots on adjacent dot triads Measured in millimeters Commonly include 39mm 35mm 28mm 26mm 25mm Note The lower the monitor s dot pitch the smaller the distance between the dot triads The lower the number the better the picture quality For example a monitor with a 28mm dot pitch is better than one with a 35mm dot pitch Monitor Terminology and Theory Dot Pitch Video Figure 3 Monitor Terminology and Theory Aperture grill Used in Sony Trinitron monitors as an alternative method to the shadow mask using very fine vertical wires instead of holes Allows more electrons to reach the screen producing deeper color intensities Requires horizontal stabilizing wires to keep the fine vertical wires from vibrating or moving and these can be viewed on bright images Dot pitch is relevant to horizontal direction only as the phosphor is coated in vertical strips rather than dots Some high quality CRTs using the aperture grill reach a dot pitch smaller than 22mm Minimum acceptable dot pitch for the aperture grill is 25mm Some dot pitch descriptions include Grill pitch horizontal mask pitch and mask pitch Monitor Terminology and Theory Aperture Grille Video Figure 4 Monitor Terminology and Theory Resolution The maximum number of pixels of a monitor Illustrated by two values separated by an x meaning by Example of a monitor resolution is 640 x 480 640 of pixels that fit horizontally or across the screen 480 of pixels that fit vertically or up and down on the screen SVGA is often described as 800 x 600 and UVGA as 1024 x 768 not definite but generally accepted by the industry this way Depends on the combination of the monitor and adapter Note The higher the monitor s resolution the smaller the pixel appears on the screen Picking a higher resolution will make Windows icons appear smaller This is often misunderstood with many users setting their resolution too high relative to their monitor size making the icons appear too small Monitor Terminology and Theory Recommended Resolutions Video Table 2 Monitor Terminology and Theory Refresh Rate The maximum number of times a screen is scanned or redrawn in one second measured in Hz Pixels do not stay excited very long and must be refreshed to stay lit The electron beam starts from the top left corner and moves horizontally to the right at the end of the row it turns off briefly and moves to the left of the next row down until the necessary pixels on the whole screen have been energized again The video card directs this motion and instructs it on which pixels need to be lit again Horizontal scanning frequency HRR or Horizontal Refresh Rate The speed which the beam traverses the screen and draws one line Measure in kilohertz kHz as determined by the video adapter Range from 35 to 90 kHz Monitor Terminology and Theory Vertical scan rate VRR or Vertical Refresh Rate The number of times the electron beam draws from the top left corner to the bottom right corner and back again to the top left drawing the entire screen Determined by the capabilities of the video adapter and the monitor Multi scan monitor also multi synch or multiple frequency Can lock onto different vertical and horizontal scanning rates More flexible because they can connect to a variety of adapters Interlacing A monitor that uses interlacing scans first odd