Perhaps you've already purchased a computer, or you're thinking about purchasing a new one. If you have any experience shopping for a computer, you know that the most expensive single component other than the computer itself is the monitor, the display screen which the computer uses to display text and graphics. You may be tempted to reduce that cost by purchasing a monitor which is physically small, or which doesn't support high resolutions and refresh rates.
You should resist that temptation! Although a quality monitor is expensive, it is also the safest investment of your money. Monitors do not become obsolete as quickly as other computer equipment. Technological advancement in hard disks, CPUs, CD-ROMs, and printers is very rapid, and a component of that type purchased today will be completely superseded within 18-36 months. But a quality, mid-priced monitor will last for many years of productive use, and will usually follow you as you upgrade from one computer to the next.
Another important factor in choosing a monitor is resolution. A monitor image is made up of'pixels', or picture elements. Pixels are either illuminated or not; the pattern they show is what makes up the image:
In the diagram above, the letter'A' is shown in pixels. Each pixel is turned on or off to make up the image. The entire image on a computer screen is made up of pixels. The resolution of the monitor is determined by the number of pixels on the screen. The higher the resolution, the more pixels, and the more space you have on your desktop for letters, numbers, windows, and images. The lower the resolution, the lower the number of pixels, and the less space you have available on your computer's desktop.
Resolution is measured in two ways. The first is'dot pitch', usually given as a fraction of a millimeter. Typical dot pitches for high performance monitors range from 0.22 mm to 0.26 mm. This dot pitch is the theoretical maximum resolution of the monitor, expressed as the distance between the holes in the shadow mask or aperture grill. Effective dot pitch is also a function of the sharpness of the electron guns and the quality and spacing of the phosphors.
In general, monitors with smaller dot pitch - closer spacing of the mask holes - will produce sharper text and graphics. The second way to express the resolution is the number of horizontal pixels and the number of vertical pixels. This is expressed as a product of the form'1024x768'. The first is the number of pixels across the screen, and the second the number of pixels up and down. This practical value indicates how much apparent desktop space will be available to your operating system and applications.
The resolution can get very high, but as it does, the electron guns have to sweep over the screen more. As a result, the refresh rate is actually an inverse function of the resolution. Here's a table of the resolutions vs the refresh rate for a popular monitor, the NEC M700:
Resolution
Maximum refresh rate
640x480 120 Hz, 800x600 110 Hz, 832x624 110 Hz, 1024x768 86 Hz, 1152x870 75 Hz, 1280x1024 65 Hz.
As you can see, the maximum refresh rate drops dramatically as the resolution increases. Following the 75 Hz rule, we see that the highest usable resolution for this monitor is 1152x870, and that 1280x1024 has a low refresh rate that would only be acceptable for specialized uses, not everyday desktop use. Whether a monitor can support extremely high resolutions and high refresh rates is a function of the electronics in the monitor. The ability to display extremely high resolutions at an acceptable refresh rate will be a substantial cost premium, so you shouldn't purchase a monitor capable of much higher resolutions than you plan to use.
The final(and most obvious) feature of a monitor is the physical size of the picture tube. Standard tube sizes for consumer-grade computer monitors are 14', 15', 17', 19', and 21', measured diagonally. However, the viewable size of the monitor is usually slightly smaller, because the extreme edges of the tube are not usable for screen display due to distortion. The viewable image size should always be listed along with the tube size.
You can convert the diagonal measure to horizontal & vertical dimensions using the 3:4:5 triangle rule:
vertical measure/3= horizontal measure/4= diagonal measure/5
The retail price of the monitor will correspond most directly to the tube size. The larger the monitor, the clearer the picture will be at whatever resolution you choose to use. And in many cases, the very high resolutions are only usable on larger monitors. Regardless of the quality of a small monitor, it will never be able to show a clear picture at resolutions like 1024x768 and 1280x1024. That means you'll have to run at a lower resolution with the corresponding sacrifice in desktop space for windows & applications.
Choosing a monitor, then, will involve balancing the following factors:
Maximum usable resolution @ 75 Hz refresh rate
Viewable screen size
Other value-added features
Subjective image quality, and Price.
We have already discussed the first two elements in this list. Other value-added features might include built-in speakers, sophisticated front-panel adjustments, or special power-saving or low-radiation features. Subjective image quality can only be judged one way: by looking at a monitor in operation at a high resolution.
I can't emphasize that last point enough. To be satisfied with a monitor, you need to see that model in operation first; purchasing a monitor sight unseen is just a gamble. Look at the monitors in use by your friends, co-workers, and at the computer store. Here are some things to look for when making a subjective analysis of a monitor:
Sharpness of individual pixels,
Clarity of black text against a white background,
Clean straight lines along the edges of the display,
Uniform color without blotches,
Highly adjustable brightness and contrast
If you purchase a monitor which doesn't meet your expectations, don't hesitate to return it for a replacement. CRTs are very difficult to manufacture, and there is substantial variation in the quality of the finished product, particularly as the tubes get larger. Unfortunately, quality control is not as good as it could be, and monitor manufacturers may occasionally try to'pull a fast one' by packaging a marginal unit for retail sale. Don't be dismayed, just keep trying until you find a monitor you like.
Remember that you've got to live with and look at your monitor for as long as you own it. If you purchase a small, substandard display, all of your time in front the computer will be correspondingly substandard. But a large, bright and sharp display with high usable resolution will serve you for many years, and will not lose value like a bargain unit. The monitor is the single most important component in your computer system.
