$1,528 flat-panel monitor pales in comparison to its predecessor
- By Michael Cheek
- May 04, 1998
Sometimes the second
generation just isn't as bright as the first. That's the case with Compaq Computer Corp.'s
new flat-panel monitor.
The 14 1/2-inch TFT450 is about $1,000 cheaper than its 15-inch predecessor, the
TFT500, which earned a Reviewer's Choice designation [GCN, Sept. 15, 1997, Page
39]. But the TFT450 lacks its forerunner's crispness and consistent brightness. When I
filled the screen with a single color and looked at it straight on, the top left and
bottom were dim, while other spots were bright.
Compaq officials have said that the TFT450 is brighter than a conventional CRT. LCD
monitor makers measure brightness in nits, or candelas per square meter. A single candela
is as bright as the flame of a wax candle.
The TFT450 generates 185 nits--about twice the brightness of a 100-watt bulb--across
the display. The TFT500 generates 200 nits. In comparison, a notebook computer's LCD
display generates about 90 nits, and a CRT monitor generates 160 nits.
LCDs are backlit, meaning light passes through the image generated by the panel. In
CRTs, however, light beams actually create the image. I cannot say whether one or the
other is measurably brighter, but the TFT450 seemed less luminous than the CRT sitting on
my desk.
Unlike the TFT500, the TFT450 did not consistently match one pixel to one dot of
resolution on the LCD. An LCD pixel is the smallest element that combines red, green and
blue to create a visible point of color. At VGA and SVGA resolutions, the TFT450 tried to
fill the screen edge to edge, generating multiple pixels per dot.
To display an SVGA screen, an LCD monitor generates 1.6 pixels for every dot of
resolution. But an LCD pixel is either on or off, so the resulting image looks jagged. A
CRT monitor could balance the pixels better at this resolution.
At VGA resolution, the TFT450 worked fine, although it took a deft touch to get the
clock phasing right. Clock phasing controls the digital conversion of the analog video
signal. Exact alignment makes a sharp image throughout.
TFT450 users should load the .inf file from Compaq to synchronize the display's refresh
rate with Microsoft Windows and the computer's video card.
The display's 0.28-mm dot pitch is a little tighter than its predecessor's. The TFT450
uses frame-rate modulation to achieve more colors--one frame shows one color, and the
alternate scan delivers a second color so fast that the eye sees them blended as a third
color. I noticed no flicker from poor frame-rate modulation.
Compaq offers a software wizard to step users through setup and adjustment. My test
unit did not include the helpful wizard, but I downloaded it from the Web at http://www.compaq.com.
The TFT450 sells for $1,528, about three times as much as a CRT monitor. If space and
power constraints require an LCD display, the TFT450 might be a good choice.