international radio engineers (IRE)

In analog television, the chrominance signal and the luminance signal are used for line-by-line and frame-by-frame screen display. In contrast, computer graphics are displayed as individual pixels.

To ensure that the brightness and contrast of such graphics do not exceed the display capabilities of the screens and lead to oversaturated images, the IRE value provides appropriate guide values for the gradation of gray scales.

The IRE value is dimensionless and was used by the International Radio Engineers (IRE) for calibrating the gradation of screens. It can be used to adjust all gray levels of the gray scale. The black level has an IRE value of 7.5 and the whitelevel has one of 100. The gray values in between are highly compressed in the black area. Voltage-wise, there is the relation between the IRE value and the voltage value for the brightness signal: IRE = 1/140 mV, then 10 IRE correspond to a brightness level of 71.4 mV, the white value of 100 IRE has 0.714 V.