2.3 Depth of Field
One complaint in many 3D animations is that they look "too clean." So, what do you do? You can add more detailed textures, better lighting, softer shadows, and even radiosity. But watch any movie, and you'll see something not often put into 3D animations: depth of field. Planning a shot so that depth of field can be applied means properly setting up lights and cameras, as well as positioning subjects appropriately. Be sure to visit Chapter 7, "Staging."
Depth of field, often called DOF in computer software, can significantly change the look and feel of your shot. It can push the viewer's attention to specific subjects simply by changing the focal point. A large depth of field, often referred to as deep focus, keeps most everything in your shot clear and sharp (see Figure 2.3), while shallow depth of field leaves only a small area in focus, blurring what's in front and behind the subject (see Figure 2.4).
Figure 2.3 An image with a small diameter aperture (a high f/stop, such as f/18) provides a sharp focus throughout the image, both close and far from the camera lens. There is more depth of field in this shot.
Figure 2.4 An image with a large diameter aperture (a low f-stop, such as f/2.8) provides less (or shallow) depth of field. The objects before and after the point of focus appear blurred, calling specific attention to the subject.
Depth of field is used in many animation settings, such as a subject focusing on a distant object. Or perhaps you have modeled and textured a small insect. When it's time to render, you want to create the most life-like image. If you shot the insect with a real camera, the area around the tiny object would be out of focus. A tight close-up creates a shallow depth of field, giving your digital shot added realism.
The aperture controls not only the amount of light, but also the depth of field. The virtual camera in your 3D application often has its own aperture to match real-world settings. Although this digital version of a camera's diaphragm is merely a representation of an effect, the results can equal that of a real camera. You can use depth of field in a number of shots:
Over the shoulder talking head shots
Hand-held camera effects
And there are many more opportunities to add depth of field when creating 3D shots, which you'll see throughout this book. But are there times when you wouldn't want to have depth of field applied? Yes. Everything should be in focus for:
Group shots, such as product line-ups or crowd shots
Cartoon or cel-shaded animations
Depth of field can also be animated, at least in the digital world. For example, many shots in movies and television use rack-focus shots. These are shots that changes focus over time, perhaps from one person talking to another. The cinematographer needs to manually adjust the focus, aperture, and any other settings on the fly while shooting the scene. In the digital world, it's much easier. You can assign a focus point to your 3D camera, set an appropriate f-stop, and then simply keyframe that focus point at any desired time. Deliberately repositioning your focus to create animated depth of field can greatly improve the look and feel of your animations.