ollars lower than when we last looked at 21-inch displays (see "20 Big-Picture Monitors," January 1996 BYTE).
For this hands-on Lab Report, we tested 38 professional-quality
monitors
with nominal 17- to 21-inch screen diagonals. We ran the lot through NSTL's battery of screen-quality tests using side-by-side comparisons; evaluated ease of use and feature sets; and measured power consumption. The monitors fell into two size classes: 17-inch and 19- to 21-inch. For the 17-inch group, the average price is around $850; for the 19- to 21-inch class, the average price is just under $2000.
Picture Quality
We asked companies to send us monitors that were capable of achieving at least a 75-Hz refresh rate at 1280- by 1024-pixel resolution. (As it turned out, not all the models that we tested were able to do this.) The higher the refresh rate, the less likely you are to suffer from the eyestrain and headaches that perceived flicker can induce. While some people are more sensitive to flicker than others are, 75 Hz is high enough for most people.
Larger monitors shoul
d have higher refresh rates because more of the image appears in your flicker-sensitive peripheral vision. Cornerstone's Color 50/115 and ViewSonic's P815 can both support an 87-Hz vertical-refresh rate at 1600 by 1200 resolution -- if you can find a graphics card that's able to drive that high a pixel rate. (We didn't test the monitors at this resolution.) These two monitors do this by pushing scanning frequencies to new levels -- up to a 115-kHz horizontal scan rate and a 250-MHz video bandwidth (see the sidebar "The Pause That Refreshes"). Both monitors support an amazing 1800 by 1440 screen resolution. But supporting these rates is electronically challenging, which accounts for the monitors' high prices (around $2200).
Different monitors often have the same picture-tube manufacturer; approximately two-thirds of the tested models incorporate either Hitachi or Sony tubes, for example. But that doesn't mean that they provide the same image quality. The electronics that produce and control the image-paint
ing electron beams have a big effect on picture quality, and there can be great differences between designs that use the same tube.
In addition, there are two basic tube types that affect image appearance, based on the type of shadow mask used to make each beam strike the correct color phosphor dots (red, green, or blue). The most common tube type uses a metal screen (a thermally stable Invar alloy) that's laced with dots that correspond to similarly arranged phosphor dots on the inside of the glass screen. Also common is Sony's Trinitron design (now licensed by other companies), which employs an aperture grille -- a vertical array of wires stretched across the screen that shadows vertical lines of colored phosphor.
Some people prefer dot-shadow masks for their pixel uniformity, while others prefer aperture-grille designs for their high contrast. Overall, the aperture-grille tubes did well in our image-quality tests.
Electronics have also made monitors easier to use. Most models now have advanced
controls with on-screen menus for adjusting the picture just the way you want it. You can often adjust such things as pincushioning, barrel distortion, and color matching. Some monitors even provide focus and convergence adjustment, important because large monitors slip out of their best adjustment setting over time.
Power and Configuration
Large monitors use lots of power -- more than any other device on your desktop. We measured power-consumption values ranging from 79.8 to 128.5 W, in active mode with a full Windows screen. All tested monitors have built-in Video Electronics Standards Association (VESA) Display Power Management System (DPMS) electronics, a feature that allows the host system to switch the monitor to a low-power mode that consumes less than 30 W, or into a sleep mode, where the monitor consumes less than 8 W. With few exceptions, we found that the monitors power down as advertised.
All tested monitors provide Windows 95 Plug and Play support, and we had no prob
lems setting them up. Plug and Play monitors support the Display Data Channel (DDC) specification, so the monitor and the host computer's graphics card and OS can all communicate. The end result is that the monitor can provide Win 95 with the resolution and refresh-frequency combinations it supports, and you get the most flicker-free mode at a given screen resolution.
In addition to the standard 15-pin D-sub cable interface, some monitors have BNC connectors that accept video signals over a set of coaxial cables, often one for each video signal (red, green, blue, vertical sync, and horizontal sync). Coaxial cables reduce signal noise by shielding the video-input signals from each other and from extraneous electromagnetic noise. If you use BNC cables, however, you don't get Plug and Play.
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Big Screens for Big Jobs
