Cinematography-Theory-And-Practice

How Not to Get More Depth-of-FieldAs a result of the basic principles of physics, wide-angle lenses willhave more depth-of-field at a given f/stop. Here we must dispelone of the most persistent myths of filmmaking. Many people stillbelieve that if you are having trouble getting the important elementsin focus, the answer is to put on a wider-angle lens and you will havegreater depth-of-field. This is technically true, but in actual practice,they then move the camera forward so they have the same framesize. The actual result? You end up with exactly the same depth-offieldyou started with! This is because you have moved the cameraforward and end up with same image magnification. It is image magnificationthat is the critical factor. You are decreasing subject distanceand increasing image magnification, which decreases depth-of-field.Hyperfocal DistanceFor every focal length and f/stop there is a particular focus distancethat is special: the hyperfocal distance. This is the closest focus distanceat which both objects are at infinity and closer objects are in focus. Whena lens is set at the hyperfocal distance, everything from 1/2 of thehyperfocal distance to infinity will be in focus.The formula for hyperfocal distance isF2H =f x CcF = focal length of lensf = f/stop numberCc = circle of confusionThere are two ways of defining hyperfocal distance.Figure 14.9. Before shooting CitizenKane, cinematography Gregg Tolandhad used deep focus on other films,including The Long Voyage Home.optics & focus277