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Image Quality Factors

When retailers advertise monitors for sale, they often include only a few specifications: the model number, size, and sometimes the viewable size and dot pitch. A monitor is one component that cannot be reliably purchased only based on the numbers--its quality is based on how it looks and this is not something that can be easily translated to figures, or even pictures. This section discusses some of the other subjective aspects of image quality that need to be considered when evaluating a monitor.

I want to emphasize: buying a monitor without seeing it in person is basically asking for trouble unless you are absolutely sure you are buying a high-end brand and that you will like it. Even then, personal taste can mean one person's dream monitor is another person's dog. You can take someone else's word for it, but this is never a substitute for seeing the monitor in living color, especially considering the cost involved here.

These are some of the other factors that influence the quality of the image produced by the monitor, and therefore, how well it will do the job for you. Many of these require testing by bringing up text or graphics on the screen to see what they look like:

• Sharpness / Focus: One of the most important quality factors is how sharp images are. Virtually every decent monitor will produce a sharp image at lower resolution and in the center of the screen. Better ones will also produce sharp images at higher resolution and in the corners. If you bring up graphics or text in the corners and the focus is noticeably worse than similar images at the center, the monitor is probably of lesser quality. (If the monitor has a focus control however, make sure it is properly adjusted. Showroom floor monitors at retail stores are sometimes mercilessly tinkered with.)
• Maximum Brightness: Some monitors are limited in the maximum brightness level they can be set to. This can sometimes be a problem when using the monitor in a bright room. Also, the overall brightness level of the CRT will tend to decrease over time, so starting out with a bright monitor is better than a dim one.
• Straightness: Vertical lines should be vertical, and horizontal lines horizontal. This isn't always the case, especially near the edges of the screen, where lines may bow inward or outward. Some monitors have a "pincushion" control that can be used to correct for this, but many do not.
• True Aspect Ratio: Most monitors use a 4:3 aspect ratio, matching the aspect ratio of most popular screen resolutions. This is done to ensure that objects have the proper proportion of height to width. If you draw a circle using a graphics program (like Paint), it should appear as a circle, and not as an ellipse.
• Glare: Monitors employ different chemical treatments and other techniques to reduce or eliminate surface glare. Glare, especially from overhead fluorescent lighting, can cause eyestrain and fatigue. Monitors that use a Trinitron CRT are vertically flat, which can reduce glare.
• Distortion: Many cheaper monitors have noticeable image distortion at their edges.
• Color Purity: A full screen of red, green or blue should appear red, green or blue. If you've ever gone to a retail store with a wall of television sets all showing the same channel, you've seen how dramatically different colors can appear on different screens. The same is true of monitors to a lesser extent.
• Monochrome Purity: Some monitors do a poor job of displaying black text on a white background, or vice-versa: they can show color at the edges of letters. Since this is something you will probably be doing quite a bit, especially if you do word processing, it's important to check.

Next: Magnetization and Degaussing

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