Follow these steps to properly adjust your monitor.
Turn your monitor's Picture control to minimum to display a black picture.
The
minimum setting of the Picture control causes the picture content to disappear
entirely. If your monitor's picture cannot be made to vanish, then you will
have to arrange to display a picture that is substantially black (for example,
by activating a screen-saver).
Turn your monitor's Black Level control to adjust black correctly.
Turn
the Black Level control to the balance point or threshold. The threshold is
low enough that a black area of the picture emits no light, but high enough
that setting the control any higher would cause the area to become a dark
gray.
Turn your monitor's Picture control to adjust the brightness level.
Once
the black level is set correctly, the Picture control can be adjusted so that
a white signal produces the appropriate level of brightness. There is no proper
setting of this control; it depends entirely on your preference.
Avoid setting your monitor too bright. Excessive brightness can increase your sensitivity to flicker, reduce the contrast ratio of the picture, and defocus the electron beam of the CRT, resulting in poor sharpness.
You may need to iterate between the Black Level control and the Picture control a few times to set the combination that both reproduces black correctly and white at the brightness you desire.