ABSTRACT
Before we go any further let us define a circle of confusion. The correct circle of confusion is the diameter of the largest dot on the recorded image that will still look sharp to the audience in the most taxing presentation venue in which that picture will ever be shown. The principle is that if you try and photograph an infinitely small dot, how large would you allow that dot to grow as it becomes less well focused on the image plane and at what size will it appear to the audience to be out of focus.
