Comparison Dell S2721QSA 27 " vs Dell S2721QS 27 "

The vertical refresh rate supported by the monitor.

Initially, the term "sweep frequency" was used in the characteristics of CRT monitors that work with an analogue signal. By tradition, it continues to be used for LCD matrices, however, for such screens, the refresh rate is actually the frame rate. See above for more on frame rate; here we note that in this case it is not the maximum frequency that is indicated, but the frequency range supported by the monitor — from the minimum to the maximum. This allows you to evaluate compatibility with certain video cards and operating modes: the frame rate of the video signal must match the frame rate of the monitor (or at least be a multiple of it), otherwise twitches and other unpleasant phenomena are possible.

It is worth noting that the monitor usually does not support any refresh rate from the range given in the specifications, but only certain standard values — for example, 50 Hz, 60 Hz and 75 Hz for the 50 – 75 Hz model.

The horizontal refresh rate of the image on the monitor screen.

This parameter was relevant for CRT monitors, in which the image was formed by an electron beam that "ran through" each individual line on the screen and illuminated the pixels. The horizontal refresh rate described the number of lines drawn per second. However, modern LCD matrices do not use a scan, but a full-frame image. Therefore, today this parameter is rarely given in monitors, and it describes the maximum horizontal frequency in an analogue video signal (for example, via the VGA interface), with which the screen can work normally.

Static contrast provided by the monitor screen.

This value describes the difference between the brightest whites and darkest blacks that the screen is capable of producing. In this case, unlike dynamic contrast (see below), the difference is indicated on the condition that the brightness of the screen backlight remains unchanged. In other words, this is the contrast that is guaranteed to be achievable within one frame. Static contrast is inevitably lower than dynamic. However, it is she who describes the basic capabilities of the screen.

The minimum static contrast ratio for tolerable image quality is considered to be 250:1, but even the most modest modern monitors give out about 400:1 (and a value of 1000:1 is not the highest class), and in high-end models this figure can reach 2000:1 and even more. .