Compared to the iPhone 4, the new iPhone 4S brings very few changes in terms of external appearance, but even so, the changes implemented by Apple could prove to be problematic for users. The Mute button was moved lower so that some cases became incompatible with the new device, but the iPhone 4S brings another novelty, more precisely we are talking about moving a sensor positioned above the speaker near the front camera. In the iPhone 4S, the ambient light sensor was moved a few millimeters to the left so that some cases could cover it and make it non-functional.
But that was before someone noticed that Apple had made a small but somewhat crucial design change: it moved the ambient-light sensor a few millimeters to the left. That created a problem for many rugged cases that covered more of the front of the iPhone: instead of peeking out through a hole cut into the case, the sensor was now hidden behind the case.
With no light penetrating, the sensor thinks the phone is in a darkened room and automatically dims the screen to look less blinding and save battery life. In the settings menu, you can manually set the screen brightness, but when in "auto-brightness" mode, the ambient-light sensor adjusts the brightness on the fly according to the ambient lighting conditions.
The ambient light sensor is the one that changes the brightness of the screen when we move from a room/space with strong light to a room/space with weak light and its coverage will lead to maintaining the same brightness of the screen regardless of our location. Case manufacturers are starting to modify their products to make them compatible with the new ambient light sensor placement and some of you may have to change your cases.
