Get your LCD in sync

Even on LCD screens with good user controls, adjusting the display for the sharpest image is difficult -- unless you know a few secrets.

I wrote last week that the new, more affordable LCD screens can be harder to adjust properly than the flat panels found in laptops, which are always digitally tuned to a particular video subsystem.

Even on LCD screens with good user controls, adjusting the display for the sharpest image is difficult -- unless you know a few secrets.

To demonstrate some of the obscure settings that can make all the difference in the new crop of LCDs, I used DisplayMate Multimedia Edition, a diagnostic utility for comparing and adjusting displays. (Go to www.displaymate.com to download various editions priced from $US69.)

For my tests, I used a KDS Rad-5 flat-panel monitor, a highly rated 15in unit with a wide variety of user-accessible controls.

Phase

One of the more important influences on the sharpness of an LCD display is a quality called phase. If this is out of adjustment, text characters and other vertical shapes appear fuzzy on their left and right sides.

Although not all LCD panels let the user adjust the phase, the Rad-5 permits settings ranging from 0 to 100 in increments of one. But I found it very difficult to hit exactly the right setting using the buttons on the unit while viewing ordinary content, such as the Windows Desktop. There seemed to be three or four sweet spots, and I couldn't find one level that seemed sharpest in all aspects.

One of the special test patterns provided with DisplayMate, however, quickly resulted in a clean image on the LCD. When I adjusted the controls while displaying a linearity phase pattern (part of DisplayMate's geometry and distortion tests) the optimum setting became obvious.

Pixel tracking

When displaying large areas of grey or other colours, LCDs can produce adverse effects called beat patterns. These cause the image to flutter, as though something is rapidly scooting left and right beneath the surface of the screen.

This visual tic can be defeated in LCDs that have good pixel tracking and timing lock. In the case of the Rad-5, an auto-level control is available that automatically adjusts the display to the output of a PC's video board.

Activating the auto-level control while displaying DisplayMate's Pixel Tracking test was all it took to lock the unit on to the video signal. The fluttering of the image became almost completely unnoticeable. If your LCD lacks an auto-level control, a manual adjustment may be available.

Grey-scale linearity

The linearity of a display can significantly affect the accuracy of graphical images. Changing the red-green-blue controls on the Rad-5 made a visible difference under DisplayMate's Linearity Check.

I'll continue this topic next week with more points on getting the image you paid for.

Brian Livingston's latest book is Windows Me Secrets. Send tips to tips@brianlivingston.com.

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