Originally Posted by chris566
It was listed under camera specs on iPad mini. I just assumed that it meant an LED like the iPhone has. So what is this feature exactly?
It's just the camera sensor and how it is manufactured. Normal sensors have some of their wiring in front of the actual light sensor which actually blocks some of the light coming through to the sensor. This method is used because it is an easier manufacturing process.
Backside illumination just means the wiring goes behind the light sensor meaning there is less to obstruct the light flow in front of the sensor and therefore this means more of the light from the scene you are imaging is captured by the sensor.
The main benefit of this method is that more light captured means less need to amplify the signal which in turn means you get less noise (grain) in the captured image - especially noticeable in poorer light conditions.