This allows you to control the angle of view of a camera interactively, by scaling a null object
on screen.

This expression will allow you to zoom a camera in After Effects using real-world focal length values.

In this Episode, Aharon shows you how to improve on and finish the binary transition project by working with Time Remapping and Camera animation. Plus, see how Magic Bullet Looks and Trapcode Shine help add the finishing touches.
By Aharon Rabinowitz

Cast 3D shadows onto live action footage
Use shadow diffusion and special material options
Tutorials for Visual Effects & Motion Graphics
Free After Effects Tutorials & More Hosted By: Andrew Kramer

Learn quick tricks of using Particular.
Attach the particular to butterflies leaving trails.
by Shoaib Khan

Interactively control camera focus distance.
The camera will focus wherever your null or solid happens to sit. This expression is golden when you're doing a lot of Depth of Field work.

Projectfile with a default camera, parented to 2 null objects and a master controller

This collection of scripts is used to transfer 3D motion to and from After Effects, Maya, Nuke, SynthEyes and Electric Image.

This expression maintains the objects apparent size as it moves away from camera.
It's helpful for taking a flat layout and making a "multiplane" layout from it for animation.

Apply this expression to your 'Scale' attribute and it'll automatically 'flip' the layer in 3d space when the camera goes behind it. This way, your text will never be seen from behind, for instance.