All levels of photographers will find something valuable in this presentation. Ron's talk will be on Depth of Field and in particular will review the concept of the circle of confusion and its relation to depth of field. Along the way he will present many photographs to illustrate the practical application of the relationships between focal length, depth of field and aperture stop. One of these relationships will be a surprise for many. Finally, he will also briefly discuss applications in macro photography and the use of tilt-and-shift techniques for the extension of depth of field.