So, the monitor’s specification says little as to how fast this monitor really is, since the dependence of the response time on the pixel’s initial and final states varies depending on the matrix types. We can’t even directly compare monitors with different matrices (for example, with TN+Film and PVA) relying just on the numbers provided by the manufacturer.
For a correct comparison we need a two-dimensional chart with a graph of the dependence of the response time on the pixel’s final state (i.e. the graph would show all possible black-to-gray transitions) or a three-dimensional graph (a surface) of the response time at all possible transitions, including those between two non-limiting states (i.e. between two shades of gray). Unfortunately, the manufacturers of matrices and monitors don’t usually offer this information.
As an example, the following graph shows the pixel rise time (Y axis) of a 25msec TN+Film matrix at transitions from black to shades of gray (X axis):
This peculiarity of LCD matrices will be first of all visible in dynamic games with a low-contrast image – the ghosting effect may be quite annoying although the formal responsiveness of the matrix may be specified to be low enough.
That said, even the time of a black-to-white transition is not a constant – it depends on the contrast setting of the monitor, and sometimes on its brightness setting, too. Generally speaking, the luminosity of a certain pixel is described as L = B + x*C, where B is a value that directly depends on the Brightness setting of the monitor, C is a value that depends on the Contrast setting, and x is the signal the pixel receives from the computer (x=0 corresponds to black color, while the maximum value of x – to white; I’m not counting gamma correction in, as I’m going to deal with it later on).
The level of contrast is controlled rather simply: the x signal from the graphics card doesn’t go directly to the matrix, but is first multiplied by the coefficient C. Thus, it is clear that white color that corresponds to the maximum angle of the crystals is only reached at the maximum contrast setting. If the contrast setting is below the maximum, the crystals will be turning around from “shut” to “almost open” and, due to the above-said reasons, this turning will take more time than what is specified by the manufacturer (who meant a “shut”-“fully open” transition).
So, here’s a general rule: reducing the contrast you increase the monitor’s response time.