Screen Specs

• Using the same materials as the windshields in helicopters and high-speed trains, the iPhone's 3.5-inch screen is both durable and scratch-resistant, despite being made of glass. Its resolution of 326 pixels per inch is the highest of any currently available smartphone at the time of publication. Resolution determines picture quality and crispness, as well as the blurriness of zooming. The iPhone also uses in-plane switching technology, which provides a clear picture from almost any angle instead of just when the viewer is looking straight at the screen.
  
  

Light Sensor

• The ambient light sensor, or ALS, detects the amount of light in the surrounding environment and automatically adjusts the brightness of the screen accordingly. It does this by taking readings, or samples, of the light that it is exposed to. The light sensor dims the screen when possible, such as in low-level light where glare is reduced, to preserve battery life. This sensor is located to the left of the earpiece.
  
  

Sensor Problems and Solutions

• If the ALS is blocked by debris or grime, it may not be able to detect light properly. Removing protective films and gently wiping the screen with a moist microfiber cloth should resolve this. The automatic brightness adjustor can also be turned off; you can check this under "Brightness" in the "Settings" app. Auto-brightness should be switched to "On," and the brightness slider should be set to the middle. After ensuring that it is on and clean, you can test the ALS by pressing the "Sleep/Wake" button to lock the phone, covering the top third of the phone to block the light and then unlocking the phone in a bright environment. The screen and icons should be somewhat dim. When you remove the cover, they should get brighter.
  
  

Software Problems and Solutions

• If the sensor is not working despite being on and clean, the problem may lie in the software. Restarting, resetting, updating or restoring the iPhone may resolve this issue. Pressing the "Sleep/Wake" button and sliding the red bar that appears shuts down the phone; pressing the button again turns it back on. Pressing and holding the "Sleep/Wake" and "Home" buttons until the Apple logo appears will reset the phone. To update the phone, it must be connected to the computer. In iTunes, the "Check for Updates" button appears in the center of the screen when you click the name of your iPhone under "Devices" on the left. The "Restore" button is directly below. Restoring your iPhone is a last resort, because it completely erases everything on the phone and re-installs the basic software, so you lose your personal settings and data. If none of these options help, the problem lies in the hardware, which requires the attention of an Apple specialist.