Sensor Blur Filter

The camera image sensor is a sandwich of three layers. The first layer is an optical Blur Filter. The light from the lens is deliberately blurred a little to better distribute the light to the sensor image elements. This is because only part of each image sensor pixel area is allocated to detecting the light.

Caveat

The blur of this image was created in Photoshop just for visual effect as there is not way to photograph the actual effect.