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Change Camera Parameters
When a camera is selected from the Actor List at the top of the Document Window or the Parameters/Properties palette, you can access its parameters and properties. The parameter dials offer several additional controls that aren’t available within the Camera Controls.

Changing Perspective
Perspective gives the effect that the scene is receding into a converging point in the distance. The Perspective value is tied to the Focal Length value (or simply Focal in the Parameters palette). The focal length is the distance from the camera where the camera is in focus.

Focal Length values are measured in millimeters that correspond to lens values on cameras. Low Focal values like 24mm and 10mm represent wide-angle lenses that are good for crowds and scenery shots. At extremely low Focal and Perspective values, the scene objects can appear distorted, as shown in Figure 6-14. Higher Focal values like 85mm and 110mm represent a telephoto lens that is focused tightly on close details. The Focal and Perspective values have no effect on orthogonal cameras. The Focal Length and Perspective values can be set using the Camera Controls or the parameter dials.

To get a quick idea of how much perspective is in the current scene, look at how square the ground plane is. As a general rule, use a 110mm Focal value for head and shoulder portraits, 35mm for standard scenes and crowds of people, 28mm for scenery and landscape scenes, and 16mm for a fisheye effect.

[Figure 6-14] Distorted perspective

Creating Depth of Field
A depth of field effect occurs when the camera is focused on a specific point in the scene and all other points closer or farther from this point appear blurry. The larger the distance from the focal point, the greater the amount of blur. The Focus Distance parameter lets you interactively set the focal point for the scene, by dragging a set a crosshairs about the scene.

While you’re changing the Focus Distance value, the Focal Distance Guide appears to help you position the focus point. Enable the Display, Guides, Focal Distance Guide menu to toggle this guide on.

Another parameter that impacts the depth of field effect is the F-stop. This parameter sets the size of the camera’s aperture. Cameras with a larger aperture let more light in when the image is captured. Setting the F-stop value to a low value causes the blurring for objects positioned away from the focal point to be more pronounced. Higher F-stop values reduce the blurring effect.

[Figure 6-15] The F-stop value affects the intensity of the blur for the depth of field effect.

Another way to think of the F-stop value is as a radius that surrounds the focal point. Lower F-stop values cause only a small area around the focal point to be in focus, while larger F-stop values increase this area, enabling more of the scene to be in focus. The radius of the area in focus is also impacted by the Focal Length value that defines the range of the scene within the camera’s view. In Figure 6-15, the image on the left uses an F-stop value of 0.4 and the image on the right uses an F-stop value of 6.4. Notice how changing the F-stop value affects the depth of field effect.

To see the depth of field effect, you must enable the Depth of Field option in the Render Settings dialog box. More on the Render Settings dialog box is covered in Chapter 16, “Rendering Scenes.”