Use "hot keys" that are assigned to functions of increasing and decreasing brightness - these two operations are separated in laptops. One of the keys included in both combinations - Fn, and the other two each manufacturer of a portable computer chooses at its discretion. For example, if you have a laptop Asus, to increase the brightness, press Fn + F6, to decrease is Fn + F5. The desired function button must be marked by a corresponding symbol - usually the symbol of the sun, supplemented by plus and minus buttons, multi-directional triangles or just two suns of different sizes.
Another way to change brightness is using the appropriate control of the operating system, which runs the laptop. In Windows 7 to cause it to appear on the screen press the Windows key, type "ele" and click the line "Change power plan" in the displayed set of links.
In the applet window using the sliders to the right the inscription "to Adjust the brightness of the plan" set the desired brightness. These two controllers here - one allows you to specify a parameter value for a laptop that is connected to an external power source, and the other adjusts the screen brightness when running on batteries. Complete the process by pressing the "Save changes".
If your laptop has a light sensor, using the settings Windows can be set to automatically change the brightness of the screen depending on its "exposure" - in the dark the brightness will decrease, the sun will increase. To find out whether there are sensors in your laptop, click on the link "Change advanced power settings" in the applet window "control Panel".
The window will contain the presets, divided into sections, each of which is revealed by clicking on the plus sign to the left of its name - open section "Screen". If it has a setting called "Enable adaptive brightness", it means that the laptop has the necessary sensors, and the version of Windows that allows you to use them. Set the value to "On" in rows relating to the mains supply and from the battery, and then press the OK button.