The focal depth of microscopes is limited. Thus an object with height structures is displayed often not  completely focused. Only those parts of the picture lying within the focal depth are displayed sharp. To display all parts of such an object one has to make a series of images, starting from the top focus plane and stepping slide by slide to the bottom.

The extended focal depth module of PicEd Cora allows to combine the slides of different height to an image where all parts are focused.