Contrast and contrast measurement with passive LCDs

An important parameter in the assessment and optimization of LCDs is the contrast value. If the contrast is too low, the picture appears pale and dull. However, if the contrast is set too high by increasing the VLCD, shadows or streaks may appear, the picture is overdriven and burn-in effects may remain.

In general, the higher the contrast value, the better the appearance. However, as the contrast value increases, the difference is no longer really perceptible to the human eye. It therefore makes sense to set minimum values for the contrast to define a lower limit; maximum values are not necessary.

Contrast measurement

The contrast increases depending on the VLCD voltage of the LCD until it drops again after a peak. This optimum must be found and the display adjusted accordingly

The measurement is carried out using suitable measuring equipment with brightness sensors, preferably in a darkened room or with the display covered. The values given in the examples refer to the respective measuring equipment and are not absolute values. The values may vary depending on the measuring tool used. In the case of fixed minimum values, the measuring equipment used must also be defined and calibrated regularly.

Influence of lighting

The influence of the backlight on the contrast is only very limited. Although brighter lighting improves the bright area, an LCD with poor contrast retains this. If the contrast behavior of an LCD is fundamentally poor, the cell must be improved.

Further information: Sensor Partners, Heise Online