How to Make the Screen Brighter on a Mac Computerby Wendy Rose Gould ; Updated September 28, 2017
Whether you have a MacBook or an iMac computer, adjusting the brightness on your screen is a simple process. A brighter screen is ideal if you're editing pictures or watching a movie on your computer. It can also come in handy if you have poor sight or simply want a more vibrant screen. Keep in mind that the brighter your screen is, the faster it will use more power. While this doesn't affect an iMac as much (you'll just use more electricity), the battery on your laptop will drain faster.
Click on the Apple icon in the top left corner of the screen and scroll down to "System Preferences" and open it.
Double-click on the "Displays" button. It is located under the hardware section of the "System Preferences."
Locate the adjustable bar entitled "Brightness" at the bottom of the window. Move it to the right to increase the brightness and to the left to decrease it. Your Mac computer's brightness will adjust as you do this.
Exit out "System Preferences" once you're satisfied with the brightness level. The setting will automatically save.