In a digital camera, a light sensor that flips over the plate with the individual light receptors and associated electronics, so that the incoming light does not have to pass through the electronics to get to the receptors. This results in a sensor with much better low-light sensitivity. A standard sensor has the electronics in front of the receptors simply because this is the easiest way to manufacture them. Manufacturing a BSI sensor is much more complex, as it requires (i) the addition of an extra silicon layer and (ii) thinning the existing one to improve its transparency.