You can adjust your laptop or desktop computer monitor's brightness in several ways, depending on your operating system, software and hardware. Apple computers and many other manufacturers use hot keys for easy screen brightness adjustments. For all PCs running Vista or Windows 7, you can find the screen brightness adjustment in the power options settings. Both methods work equally well, so you should use the one that is more convenient.
Press the "Sun" button with a down arrow icon, dark spot or other indicator that the key is used for dimming the screen. On Apple computers, this is usually all you need to do to lower the screen light.
Press the "Function" or "Fn" key on your keyboard (usually in the lower left corner) and hold it down while you press the dimming function key described in Step 1, if the key does not work on its own. Some Windows computers require holding the "function" or "Fn" key down to trigger the function keys.
Press the button repeatedly until the light is dim enough to suit your needs.
Click "Start," "Control Panel," then "Hardware and Sound." The screen light is part of the hardware and controls how the computer uses its power. This is why it appears in this section of the control panel rather than with the display settings.
Click "Power Options" to open the Power Settings window.
Click on the screen brightness slider near the bottom of the window and drag it to the left to dim the screen. Release the mouse button to view the change. Continue dragging it as far to the left as necessary to lower the light on your screen to your liking.
Close the window when you are finished. The computer will retain your brightness setting until something alters the power configuration, such as switching from battery to AC power or restarting the computer.
Permanently lower the light on your monitor for the computer's power plan by clicking "Change plan settings" in the Power Options window. From there, you will see individual sliders to adjust your monitor light when the computer is running on battery (laptops only) and AC power. Drag each slider to the left to lower the screen brightness to your desired level for that power setting. Click "Save changes" to finalise the new settings.