LCD Technicalities: How Important Are Contrast Ratios?
We're making a few changes in the format of our LCD screen articles. Let's begin with the good news, there'll be more comparison tests and more screens tested this year. The aim is to achieve one comparison test per month. The second change is that the technical stuff will be communicated in specially dedicated articles. This is the first article in the new technical series.
Problem No. 1: Response Time
The "Everything and Anything" series began with the previous LCD 17" screen comparison test . We stressed the absurdity of measuring the response time, showing how little it represented, and how it could mislead potential buyers.
We then explained that the current response time value, measured in black and white, then a return to white, was not necessarily representative of the response time from one color to another, from white to gray, from gray to black, from purple to yellow, etc. In fact, two screens both quoted as having a response time of 25 ms could behave completely differently, depending on the color change. The values, thus, means very little.
Furthermore, the measurement was not, in fact, a true one because it was merely the measurement of a signal that was truncated at each end. While truncating the signal at each end served to facilitate gauging the response time, it concealed defects in the stability of the liquid crystals and might hide a slow reaction to stimulation.
If you want more information on the subject, what we wrote a few months ago still holds true: read about it here .
Problem No. 2: 18- And 24-bit LCD Screens
The same section raised issues about color interpolation. You need to be aware that not all LCDs are necessarily capable of reproducing 16.7 million colors. Many of them, and the majority of entry-level monitors, make do with 262,144, to which dithering, rapid color changes, is added.
All the explanations about 18 and 24 bit matrices and their consequences can, once again, be found here .
