Defocus is the aberration in which an image is simply out of focus. This sort of aberration would be familiar to anyone who is has used a ' camera, video camera, microscope, telescope, binoculars '. This will give the effect of a multiple number of lights but shown in a way that is left more for the viewer to imagine what is going on and what the lights are coming from. In simple terms defocus reduces the sharpness and contrast of the image. What would originally be sharp high focused edges would then be changed into very rounded unfocused edges.