Specifications
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Chapter 15 Video Hardware
Note
Because CRT monitors are redrawing the screen many times per second, the change in a noninterlaced CRT screen dis-
play is virtually invisible to the naked eye, but it is very obvious when computer screens are photographed, filmed, or
videotaped. Because these cameras aren’t synchronized to the monitor’s refresh cycle, it’s inevitable that the photo, film, or
videotape will show the refresh in progress as a line across the picture.
If you need to capture moving images from a monitor to videotape, use a video card with a TV-out option to send your
picture to a VCR. If you need to take still photos of a monitor (for example, to record BIOS/CMOS setup information), use
an LCD display instead of a CRT monitor.
In my experience, a 60Hz vertical scan frequency (frame rate) is the minimum anybody should use with a
CRT, and even at this frequency, most people notice a flicker. Especially on a larger display, onscreen
flicker can cause eyestrain and fatigue. If you can select a frame rate (vertical scan frequency) of 72Hz or
higher, most people are not able to discern any flicker; 72Hz is the minimum refresh rate I recommend.
Most modern mid-range or better CRT displays easily handle vertical frequencies up to 85Hz or more at
resolutions up to 1024×768. This greatly reduces the flicker a user sees. However, note that increasing the
frame rate, although it improves the quality of the image, can also slow down the video hardware because
it now needs to display each image more times per second. If you’re a gamer, slower frame rates can
reduce your score. In general, I recommend that you set the lowest frame rate you find comfortable. To
adjust the video card’s refresh rate with Windows 9x/Me/2000/XP, use the Display icon in Control Panel.
Depending on your flavor of Windows, the refresh rates supported by the video card will appear on one
of the Display tabs. Optimal is the default setting, but this really is a “safe” setting for any monitor. Select
a refresh rate of at least 72Hz or higher to reduce or eliminate flicker. Click Apply for the new setting to
take effect. If you choose a refresh rate other than Optimal, you might see a warning about possible moni-
tor damage. This is a warning you should take seriously, especially if you don’t have detailed information
about your monitor available. You can literally smoke a monitor if you try to use a refresh rate higher
than the monitor is designed to accept. Before you try using a custom refresh rate, do the following:
■ Make sure Windows has correctly identified your monitor as either a Plug and Play monitor or
by brand and model.
■ Check the manual supplied with the monitor (or download the statistics) to determine which
refresh rates are supported at a given resolution. As in the example listed earlier in Table 15.6,
low-cost monitors often don’t support high refresh rates at higher resolutions.
Click OK to try the new setting. The screen changes to show the new refresh rate. If the screen display
looks scrambled, wait a few moments and the screen will be restored to the previous value; you’ll see a
dialog box asking whether you want to keep the new setting. If the display was acceptable, click Yes;
otherwise, click No to restore your display. If the screen is scrambled and you can’t see your mouse
pointer, just press the Enter key on your keyboard because No is the default answer. With some older
video drivers, this refresh rate dialog box is not available. Get an updated video driver, or check with
the video card vendor for a separate utility program that sets the refresh rate for you.
If you have a scrambled display with a high refresh rate, but you think the monitor should be capable
of handling the refresh rate you chose, you might not have the correct monitor selected. To check
your Windows 9x/Me/2000/XP monitor selection, check the Display Properties dialog box. If your
monitor is listed as Standard VGA, Super VGA, or Default Monitor, Windows is using a generic driver
that will work with a wide variety of monitors. However, this generic driver doesn’t support refresh
rates above 75Hz because some monitors could be damaged by excessive refresh rates.
In some cases, you might need to manually select the correct monitor brand and model in the
Windows Display Properties dialog box. If you don’t find your brand and model of monitor listed,
check with your monitor vendor for a driver specific for your model. After you install it, see whether
your monitor will safely support a higher refresh rate.
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