One of the most popular types of lenses used in video production is the zoom lens. These types of lenses can be continuously varied throughout the entire focal length range from the widest to the narrowest. A zoom lens keeps the video or film professional from having to lug 20 different lenses with them on a shoot. While you don't have to change lenses in 3D space, most of the 3D programs on the market allow you to keyframe the focal length over time, thus creating a zoom lens effect. Click on image 7 to view an animation of a zoom lens in action, and notice the distortion that occurs as the camera moves from a wide angle to narrow angle lens.

If you are trying to emulate the real world, a good place to start is by watching movies and television shows. Depending on the genre, you will see different ways in which these lenses are used. Army of Darkness has a total different look than Star Trek, which has a different look than 2001: A Space Oddesy. Each look is not only attributed to set design, lighting, etc., but also to the types of lenses that are used to shoot each scene.

Defining the different types of lenses available to you should be enough to get you experimenting with ways to improve your shots, but there are a couple other areas we need to discuss if you want to really duplicate the properties of real world lenses.

F-stop
The aperture or iris of a camera lens is very similar to the way our own eye works. When it is dark, our iris opens to allow more light in, and when there is too much light, like a bright sunny southern California day, the iris closes to allow less light in.

On a camera, the various openings on the iris have been calibrated in a numerical system called f-stops. An f-stop is a ratio between the aperture opening to the diameter of the lens. These calibrated settings generally range between f/1.4 to f/22. The larger the number, the smaller the iris opening, and vice versa. Each time you move up or down the f-stop setting, the amount of light that enters the camera is either doubled or halved depending on which way you go. For example, going from f/1.4 to f/2.8 decreases the light by one half, and going from f/5.6 to f/4 doubles the amount of light entering the opening.

On a typical day, shooting outside with a video camera, your f-stop will generally be set to f/5.6 or f/4. I think you will find that many of the 3D packages have their default f-stop at f/4.

Also, it is important to note that increasing or decreasing the f-stop in your animation program does not have an effect on the overall exposure of your animation, but instead plays a key roll in depth of field. This can be a good thing or a bad thing, depending on your view of the world.