Focal Length

The distance between the lens and the light-sensitive surface, whether film or video electronics, is called the focal length of the lens. Focal length affects how much of the subject appears in the picture. Lower focal lengths include more of the scene in the picture. Higher focal lengths include less of the scene but show greater detail of more distant objects.

Focal length is always measured in millimeters. A 50mm lens is a common standard for photography. A lens with a focal length less than 50mm is called a short or wide-angle lens. A lens with a focal length longer than 50mm is called a long or telephoto lens.

Field of View (FOV)

The field of view (FOV) controls how much of the scene is visible. The FOV is measured in degrees of the horizon. It is directly related to the focal length of the lens. For example, a 50mm lens shows 46 degrees of the horizon. The longer the lens, the narrower the FOV. The shorter the lens, the wider the FOV.

Relationship Between FOV and Perspective

Short focal lengths (wide FOV) emphasize the distortions of perspective, making objects seem in-depth, looming toward the viewer.

Long focal lengths (narrow FOV) reduce perspective distortion, making objects appear flattened and parallel to the viewer.

The perspective associated with 50 mm lenses appears normal, partly because it is close to what the eye sees, and partly because such lenses are so widely used for snapshots, news photos, cinema, and so on.

Differences Between Camera Objects and Real-World Cameras

Many other controls on real-world cameras (such as those for focusing a lens, and advancing film) aren’t needed for computer rendering and have no counterpart in the camera objects.

3ds Max does have counterparts for the camera movements used in movie making, such as truck, dolly, and pan. See Camera Viewport Controls.

Procedures

To match a real-world camera frame proportion:

1. Choose Rendering Render Setup.

   The Render Setup dialog opens.

2. In the Output Size group, click the arrow to display the list of real world output sizes.
3. Select the type you want (both film and video output sizes are available).
4. Click or right-click the Camera viewport label, and turn on Show Safe Frames.

   The Safe Frame proportions will match those of the selected output size.