19'' LCD survey : 2, 3, 4, 6, 8 ms and above (page 1: Introduction)

LCD 19" survey: 2, 2,4, 3, 6, 8, 12, 18 ms

This LCD survey is the last of 2005 and in fact it´s better to see it as the first of 2006, because the monitors tested here are just beginning their product life. All of them haven´t even all hit stores yet. They will start out untarnished products and consumers will only really be familiar with them in the months to come when their reputations are established. By then everyone will be aware that monitor response times have fallen under 3ms and know without any hesitation if it is best to choose a TN, VA or IPS.

To begin with, here is the list of the screens to be tested and a few basic facts to refresh your memory.

Today´s menu

There are TN, MVA, S-PVA and S-IPS monitors. All types of technology and response times are here! If the monitor you have been dreaming of isn´t amongst these, you can at least look for an equivalent product. We tested 8 new LCDs and there are five previously tested ones for comparison in some of the tests (color and/or reaction time).

Beginning to decode

Three big families are represented in this survey with response times of 2 to 18 ms.

The first mistake would be to fully trust the claimed response time figure. A 6ms monitor isn´t necessarily bad for games compared to a 2ms, which is supposedly 3 times faster. The main interest of this value is to place product generations within each panel type.

For example, 3ms panels are in principle more recent than 4ms. It doesn´t mean, however, that:

- they are actually faster than the 4 ms,
- they are more recent than another technology´s 8ms response time panels .

Also, manufacturers use gray to gray response times, and sometimes a second measurement between black and white. These often differ, proof that response time can vary from one color to another. It isn´t the same going from light yellow to dark blue or from red to pink. Ideally, it would be necessary to measure all grey to grey transitions, or 256 x 256 = 65,536 measurements to have an idea of the real response time. This might be best but not necessarily enough. Manufacturers have also added a number of tricks like overdrive and dithering. The first over amplifies the liquid crystal voltage and the other flickers pixels at high speed with a reduced number of colors. In practice, this results in:

overdrive : at times a trail in front of objects in motion, which resembles afterglow in a way that it causes visual artefacts or a trail of light that shouldn´t be there. This over amplification may or may not be included in response time measurements, which by definition truncates the extreme part of the reaction. Only the signal from 10 to 90 % is included and so over amplification will be partly or totally removed. Truncating the signal to establish the measurement also neglects crystal reaction time and color stabilisation (a problem independent from overdrive bind to the response time definition). For more information on overdrive here.

dithering: a reduction of the color spectrum where all aren´t actually displayed. With TN monitors there aren´t 264 color levels, only 64. Therefore, measurements must be adapted and we have to take into account the visual consequences on screen. It can occasionally lead to a strong twinkling effect in movies, and also in games and in wide color areas. This phenomenon isn´t reported in response times.

Another trick needs, at least for some Samsung products, is image anticipation. According to this manufacturer, it makes liquid crystals react faster. In practice it can result in a ghost images in front of objects. It also isn´t included in the response times.

These three tricks were discovered in tests and not necessarily revealed by manufacturers. We don´t know if there are others, but it´s highly probable. How much consideration should we give to this figure if visual tests are in total contradiction (something we saw last year when connecting an oscilloscope and a probe to the monitors)?

This is the reason why we always also include several practical tests.

Tests

Color fidelity and calibration, game reaction time, video quality, ergonomics, viewing angles, and the quality of interpolation-every aspect of each monitor is examined.

For color fidelity we use the LaCie Blue Eye Pro colorimeter, based on the Gretag tool and coupled with the new LaCie software suite. More evolved than the previous version, this helps us to compare a monitor’s display quality (color spectrum and DeltaE) in standard settings and after calibration. Results are sometimes surprising as it’s often best to take the time to manually adjust colors (or at least contrast, brightness and color temperature).

For game tests, after developing a response time measuring procedure last year with a probe and an oscilloscope, we eventually came to the conclusion that the measurements weren’t representative of what we actually saw on the screen. The results, for example, were that a ViewSonic VP191b was much faster than the Hyundaï L90D+ TN 8 ms. After playing a game and watching a movie for five minutes with these monitors you realize that the opposite is true. We then developed a new test procedure in the summer of 2005, based on pictures of images on the monitor. In this way we can capture afterglow in two environments. The first is between bright colors and the second is for black and white (like in wire frame mode). The software used is Pixel Persistence Analyzer (or PixPerAn for regular users). Pictures showing these ghosting effects are captured with a Canon 350D at a shutter speed of 1/1000 s. We take 50 pictures in burst mode for each test to precisely measure the progression of afterglow between images. This time results are consistant with what we see in games. Finally, practical tests are the same in games, HD and DVD video, web surf etc.

The test computer is self-assembled and has an AMD Athlon XP3200+ processor and NVIDIA GeForce 6800 GT card.