X-bit labs

Xbit Labs Presents: LCD Monitors Testing Methodology Indepth (page 6)

Category: Other

by Oleg Artamonov

[ 06/10/2007 | 10:28 PM ]

RTC Error

Everything has its price, unfortunately. Endowing modern matrixes with superb speed, the Response Time Compensation mechanism has one drawback. It works by sending a special overdrive impulse to the LCD cell (follow the link at the beginning of this article to read more about how RTC works). If the overdrive impulse is too strong, there may appear a new kind of image artifacts that cannot occur on matrixes without RTC: a dark object moving on a light-gray background is leaving a short white trail (in the traditional “ghosting” effect the trail is dark, not light).

We measure the value of the RTC miss in percent. For example, if the pixel brightness should have changed from 0 to 100, but was actually increased to 150 due to an RTC miss and then returned to 100, the value of the miss is 50%. The results are shown as a 3D histogram, just like the response time diagram, separately for each transition.

These numbers have two meanings. First, the grosser the miss, the more different the pixel brightness is at its peak from the desired level and, accordingly, the more conspicuous it is for the eye. Second, the grosser the miss, the longer it takes the pixel to fall back to the desired level, which makes the artifact more conspicuous, too.

Of course, we publish the average value of the RTC errors. If it is below 5%, you are unlikely to notice any RTC artifacts. If within 5-10%, there are artifacts, but not very annoying. If above 10%, the artifacts are going to be visible to the eye.

However, the level of annoyance depends on your personal perception here, like with many other things.