Specifications

Monitor Selection Criteria
891
Horizontal Frequency
Different video resolutions use different horizontal frequencies. For example, the standard VGA reso-
lution of 640×480 requires a horizontal resolution of 31.5KHz, whereas the 800×600 resolution
requires a vertical frequency of at least 72Hz and a horizontal frequency of at least 48KHz. The
1024×768 image requires a vertical frequency of 60Hz and a horizontal frequency of 58KHz, and the
1280×1024 resolution requires a vertical frequency of 60Hz and a horizontal frequency of 64KHz. If
the vertical frequency increases to 75Hz at 1280×1024, the horizontal frequency must be 80KHz. For a
super-crisp display, look for available vertical frequencies of 75Hz or higher and horizontal frequencies
of up to 90KHz or more. My favorite 17'' NEC monitor supports vertical resolutions of up to 75Hz at
1600×1200 pixels, 117Hz at 1024×768, and 160Hz at 640×480!
Virtually all the analog monitors on the market today are, to one extent or another, multiple-frequency.
Because literally hundreds of manufacturers produce thousands of monitor models, it is impractical to
discuss the technical aspects of each monitor model in detail. Suffice it to say that before investing in a
monitor, you should check the technical specifications to ensure that the monitor meets your needs. If
you are looking for a place to start, check out some of the magazines that periodically feature reviews
of monitors. If you can’t wait for a magazine review, investigate monitors at the Web sites run by any
of the following vendors: IBM, Sony, NEC-Mitsubishi, and ViewSonic. Each of these manufacturers cre-
ates monitors that set the standards by which other monitors can be judged. Although you typically
pay a bit more for these manufacturers’ monitors, they offer a known, high level of quality and com-
patibility, as well as service and support. Note that most monitor companies sell several lines of moni-
tors, varying by refresh rates, CRT type, antiglare coatings, energy efficiency, and warranties. For best
results at resolutions of 1024×768 and above, avoid the lowest-cost 17'' monitors because these models
tend to produce fuzzy onscreen displays with low refresh rates.
Controls
Most of the newer CRT monitors and LCD panels use digital controls instead of analog controls. This
has nothing to do with the signals the monitor receives from the computer, but only the controls (or
lack of them) on the front panel that enable you to adjust the display. Monitors with digital controls
have a built-in menu system that enables you to set parameters such as brightness (which adjusts the
black level of the display), contrast (which adjusts the luminance of the display), screen size, vertical and
horizontal shifts, color, phase, and focus. A button brings the menu up onscreen, and you use controls
to make menu selections and vary the settings. When you complete your adjustments, the monitor
saves the settings in nonvolatile RAM (NVRAM) located inside the monitor. This type of memory pro-
vides permanent storage for the settings with no battery or other power source. You can unplug the
monitor without losing your settings, and you can alter them at any time in the future. Digital controls
provide a much higher level of control over the monitor and are highly recommended.
Tip
Digital video engineer Charles Poynton’s notes on adjusting brightness and contrast controls provide an excellent tutorial
on the use of these often misunderstood monitor adjustments. Find them online at http://www.vision.ee.ethz.ch/
~buc/brechbuehler/mirror/color/Poynton-color.html.
Digital controls make adjusting CRT monitors suffering from any of the geometry errors shown in
Figure 15.9 easy. Before making these adjustments, be sure the vertical and horizontal size and posi-
tion are correct.
Tip
Get a monitor with positioning and image controls that are easy to reach, preferably on the front of the case. Look for
more than just basic contrast and brightness controls; a good monitor should enable you to adjust the width and height of
your screen images and the placement of the image on the screen. The monitor should also be equipped with a tilt-swivel
stand so you can adjust the monitor to the best angle for your use.
Chapter 15
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