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Thousand Oaks |
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Thousand Oaks |
If you're looking for a machine to run Windows, don't spend a lot of time worrying about the computer itself. Decide which class machine you want, look for the best price, with sixteen megabytes of memory and a 540-megabyte hard drive and buy it. Then put your effort and as much of your budget as you can into picking a display monitor.
There isn't very much difference between different make computers. But you'll spend your computing hours looking at the monitor, which makes it a critical choice.
Graphic-user interfaces (GUI) such as Windows put great demands on displays. Most DOS programs put 25 lines of text on the screen. A bigger display gives 25 lines of bigger text. But graphic interfaces adjust how much they cram into a window to the size of the display. Bigger screens show you more of a word-processing page or spreadsheet, or the output of several programs at once.
Even so, the best and biggest monitor won't do you much good unless you configure it properly. A video image is made up of thousands of tiny dots, or "pixels," and the key to comfortable viewing is matching the number of pixels to the monitor size. Windows leaves it up to users to choose the right screen resolution.
Monitors are growing. The 14-inch size that has been standard for several years is giving way to 15-inch units (and 17-inch units in 1998). Seventeen-inchers are becoming the choice for serious users. But unless your larger display is set up right, you'll just see bigger, grainier images.
The right resolution depends on your eyes and how far away from the screen you sit. For most users, the standard Windows display-640 pixels wide and 480 pixels high--looks just about right on a 14-inch monitor. Many users are comfortable with the next step up. 800-by-600, on a 15-inch unit. And the sharp-eyed probably can work at 1024-by-768 pixels on a 17-inch screen.
Of course, there's no point worrying about configuring your monitor until you have bought it, and careful shopping is time-consuming. I find that specifications for "dot-pitch size" and "scan rate" are next to useless in describing monitors' actual performance. You're much better off trusting your eyes and going with your personal preferences.
Some monitors offer crisp, brilliant images, but at the price of greater susceptibility to glare. Other manufacturers fight glare with coatings that dull the image slightly. Some more expensive monitors use high-tech coatings to improve the trade-off, but in the end, the choice is a matter of taste. Shopping requires looking at as many different monitors in stores as you can. Remember that dealers show monitors under ideal conditions; anything that looks less than perfect in the store will be worse in your home or office.
If you're buying a new monitor, either as part of a new system or to upgrade your old computer, you'll probably want a 17-inch model. Unfortunately, glass blowing hasn't enjoyed the same manufacturing revolution that has driven down semiconductor prices. Street prices are still relatively high. The top-of-the-line units generally offer features, such as precise color calibration, of limited value to most users, so a mid-price unit may be your best bet. Fifteen-inch monitors run about $400 less.
New software will make it easier for users to tune your display for best performance. For now, that's still harder than it ought to be. But there's probably no area of computer use where time invested in learning will pay greater dividends.
The video monitor, or video display, is the most popular methods of displaying computer data. At the heart of the monitor is the cathode-ray tube (CRT), familiar to all of us because of the television receivers we have in our homes. As a matter of fact, many computers use television sets as video displays. The basic difference between a television set and a monitor is that no radio-frequency demodulation electronics are necessary in the monitor. As an output device, the monitor can be used to display both alphanumeric characters and non-text graphics. There are two possible methods of operation used to create these displays: the "raster scan" method and the X-Y (or vector scan) method. All television sets and most video displays are of the raster-scan type.
Let's examine the basic operation of the CRT tube. Quite simply, a CRT is an evacuated glass tube, with an electron gun in the neck of the tube and a rectangular fluorescent-coated surface located opposite the electron "gun." When activated, the electron gun emits a stream of electrons, which strike the fluorescent coating on the inside of the screen, causing an illuminated dot to be produced.
The position of the beam along the face of the screen can be manipulated with the use of horizontal and vertical deflection coils that are attached to the tube, and which cause the beam to deflect due to the principles of electromagnetic attraction and repulsion. The horizontal and vertical deflection coils are usually combined in a single unit, called a yoke, which slips over the neck of the tube. By applying different signals to the different coils, the electron beam can be positioned anywhere along the face of the screen.
In the raster-scan method of creating displays, separate signals are applied to the horizontal and vertical yoke coils to cause the electron beam to move across the display screen. As the beam moves, it leaves an illuminated trace, depending on the characteristics of the fluorescent coating, which requires a specific given amount of time to dissipate. This dissipation quality is referred to as persistence.
In theory, the electron beam begins at the upper left-hand corner of the display screen and sweeps across its face to the upper right-hand corner (as you're facing the screen), leaving a line across the screen (raster). Upon reaching the right side of the screen, the trace is blanked out and the electron gun is repositioned to the left side of the screen, one line down from the first trace (retrace). At this point, the horizontal sweep begins producing the second line of the screen. This continues until the horizontal sweep reaches the bottom of the screen, at which time the electron beam is blanked again and returned to the upper left corner of the screen completing one field. Two fields make up a frame.
Video information is introduced to the picture by varying the voltage applied to the electron gun as it scans the screen. Typically, a voltage just above one volt, when applied to the electron gun's drive circuitry, produces no electron emission and a black (blank) area is created. A signal voltage of approximately three volts causes maximum electron emission and a white area is created. Voltages between one and three volts result in various levels of gray. In this manner, the electron gun "paints" the desired "picture" on the fluorescent screen by varying its intensity.
The human eye perceives only the "picture," due to the blanking of the retrace lines and the frequency at which the entire process is performed. Typically, a horizontal sweep requires approximately 1/60 of a second for a complete field, or 1/30 of a second for a complete frame. The two fields, one containing the even numbered lines and the other containing the odd numbered lines, are interlaced to produce a smooth, flickerless image.
Monitors and graphics adapters (the PC board which controls the monitor) speak to each other mainly in terms of frequencies. The graphics card sends out RGB, horizontal, and vertical sync signals to the display and the display's electron guns draw screens one horizontal line at a time, from left to right. The guns must make several hundred horizontal passes for each complete frame.
The number of lines the monitor draws on the screen per second is the horizontal scanning frequency, or line frequency. The number of frames the monitor draws per second is called the vertical scanning frequency, refresh rate, or frame rate. Bandwidth, measured in MHz, is an expression of the number of dots that a monitor can display in a line per second.
In general, the greater the bandwidth, the better the monitor. Typical band-widths for current monitors are 18 MHz for VGA models and 35 MHz for SVGA models.
Because many horizontal lines must be drawn before one vertical cycle is complete, horizontal frequency is described in kilohertz (kHz), while vertical frequency is expressed in hertz (Hz). VESA has established minimal recommended vertical refresh rates that have become standards. For 640-by-480 and 800-by-600 resolutions, VESA recommends a 72-Hz refresh rate, while for 1,024-by-768, it recommends 70 Hz.
A color monitor with a vertical scanning range of 55 Hz to 80 Hz and a horizontal range of 30 kHz to 60 kHz provides a comfortable combination of backward compatibility with an older video card and current compatibility with a new one. If you want to extend the useful life of your new monitor, buy a model with a broader frequency range--say, 50 Hz to 120 Hz vertical and 30 kHz to 62 kHz horizontal.
The trend toward multi-frequency capability (actually multiple sets of fixed frequencies) and 15-inch and larger monitors is directly linked to the rise in popularity of graphical user interfaces (GUIs), particularly Microsoft Windows 3.1.
Pay attention to a monitor's vertical refresh rate and its dot pitch. These numbers can help you avoid grainy graphics and screen flicker. Dot pitch refers to the space between the individual dots or picture elements (pixels) that make up a screen. A larger dot pitch produces a grainier, less focused image; a smaller dot pitch produces a sharper image. When shopping for a 14- or 15-inch monitor, look for a dot pitch of 0.28 mm or smaller
Sony's Trinitron picture tube does not have a dot pitch per se. Instead of using a shadow mask (as do other monitors), the Trinitron tube uses a stripe mask (or aperture grill). The space between the stripes is sometimes mistakenly referred to as dot pitch.
Even the smallest dot pitch won't eliminate the annoyance of a flickering monitor. Screen flicker results from a SLOW screen refresh rate or from interlacing, which refreshes only every other line of the screen, then fills in the remaining lines in a second pass. Some monitors flicker so badly that they can cause users eyestrain and headaches.
Non-interlaced (or progressive-scan) monitors refresh the entire screen in one pass. The easiest way to avoid screen flicker is to buy a non-interlaced monitor with a high vertical refresh rate, paired with a video card capable of the same. A vertical refresh of 72 Hz or higher almost guarantees a flicker-free screen.
Many of the 14- and 15-inch multi-frequency monitors are Multi-scanning (or multi-synchronous). Multi-scanning enables a monitor to adjust (or "sync") to whatever vertical and horizontal signals are being broadcast from the graphics adapter, provided those signals fall within the monitor's scanning range (bandwidth). Variable-frequency multi-scanning is preferable because it supports more frequency combinations, which allows the monitor to work with more video cards and at more resolutions; multiple fixed frequency is the alternative to this.
Unfortunately, there are no Super VGA scanning standards to help set guidelines, which is another reason for buying a multi-scanning monitor. Despite multi-scanning's importance, not every 14- and 15- inch monitor provides such a capability, so check for this feature when evaluating models. Multi-scanning is also called auto-syncing.
Another feature to look for in a monitor is auto-sizing, which enables you to maintain a uniform screen size when switching between modes (for example, between an SVGA Windows 3.1 screen and a VGA DOS prompt). Without auto-sizing, you might have to adjust the picture manually, which is a pain if you work in different video modes, environments, and applications.
Monitor controls have generally improved as more vendors have incorporated digital controls, which are driven by micro-processors. These let you more finely tune a monitor and also provide preset modes. Even analog controls (non-microprocessor-driven, finger-controlled wheels) have gotten better over the last year. Most monitors offer digital controls for image size and position, and analog controls for contrast and brightness. There are no significant advantage for monitors that use digital controls for brightness and contrast.
Digital image size and position controls do offer tangible advantages, most notably the ability to provide preset and customized modes. The same vendors that offer digital brightness and contrast controls also provide digital image controls.
Another feature to consider is glare control. Anti-glare treatment can improve imaging by reducing the ill effects of overhead glare, so any monitor lacking glare control as standard equipment should be looked at carefully to see if it suffers from excessive reflected room light. Many monitors provide some kind of anti-glare treatment on the screen.
Most monitors lack external degaussing controls, which enable a monitor to be reset after magnetic interference. Some other models use an automatic degausser upon startup; and a few vendors have models with no degaussing capability.
Most monitors claim MPRII. This standard defines acceptable levels (amount and direction) of extremely low frequency (ELF) and very low frequency (VLF) electromagnetic radiation emitted by monitors. The monitors that claimed MPR II compliance usually pass both ELF and VLF magnetic emissions tests. If potential dangers of ELF and VLF emissions concern you, you may want to think hard before buying a unit that does not claim MPRII compliance. Many vendors that currently do not provide MPR II-compliant monitors plan to do so in the near future, so make sure to ask.
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